SIMBA Telecom discussion thread

[Habrosus]

All the telcos need VoLTE now, unless you are lucky to have 5G SA coverage and working VoNR at all places you go, which is not possible as of now. Or you stay home and use only VoWiFi, which does not seem to be applicable to you.

Just give up on using SIMBA as the main line. Use it as a secondary line and also for roaming.

Thanks, I guess that's my only option for better line connectivity.

 

[JAYSCS]

Different location, and now it's happened again.

I was making a call from my Simba line (primary line), except that this time the data usage is set to Simba (previously Eight).

For record, Simba line shows 2/4 bars on my iPhone while Eight shows 4/4. The latter looks better, right?

While making the call (on speaker so I was able to observe the screen), the Eight line went all the way down to 1/4 bars.

This could highly be the reason why my previous call from the Simba line was cut off, when data usage was set to Eight. Simba calls need VoLTE, right? So when the Eight line went down/off, the call got cut off.

Does that mean I've to 1) use only Simba line for data usage, or 2) port this primary line out to another telco that doesn't need VoLTE for calls, so that I can set data usage to other telco lines as and when I like?

By right this should not happen, it is very weird. The beauty of 4G is that both call and data will still remain active and not sacrifice either. May be it is the phone model operation oversight of proper dual sim function? If you try to use it as single sim by removing your Eight sim card, will the problem remain? If it functions well, may be 2 phones for each sim is the way to go, or change the phone with proper dual sim operation?

 

[xiaofan]

By right this should not happen, it is very weird. The beauty of 4G is that both call and data will still remain active and not sacrifice either. May be it is the phone model operation oversight of proper dual sim function? If you try to use it as single sim by removing your Eight sim card, will the problem remain? If it functions well, may be 2 phones for each sim is the way to go, or change the phone with proper dual sim operation?

1. No matter what, eight signal strength has nothing to do with SIMBA Voice call being dropped because of weak SIMBA signal.

1) Now he is using SIMBA as default for data and voice. SIMBA Voice call will be dropped, if SIMBA signal is weak.

2) Previous case is the same, when SIMBA was set as the default for voice but eight was set as default for data. Again SIMBA Voice call would still use SIMBA 4G connection (VoLTE), not eight 4G connection.

So signal strength of eight does not matter in both cases. eight data connection cannot help for weak SIMBA signal for SIMBA voice call.

2. Why eight signal level drops from 4 bars to 1 bar during the SIMBA voice call is a separate issue. That could mean eight signal is not stable in the same place.

3. In summary: it is better to give up using SIMBA as the main number if he needs more stable network connection for both data and voice call.

 

[xiaofan]

Take note "Allow Mobile Data Switching" does not help here since it is about SIMBA voice being dropped, not the data connection of the iPhone being dropped during the voice call.

https://support.apple.com/en-sg/109317

If you turn on Allow Mobile Data Switching, then while you're on a voice call on your voice-only number, that number will switch to using voice and data automatically.6 This will let you use both voice and data while on the call.

If you turn off Allow Mobile Data Switching and you're active on a voice number that isn't your designated mobile-data number, then mobile data won't work while you're on the call.

To turn on Allow Mobile Data Switching, follow these steps:

1. Go to Settings.
2. Tap either Cellular or Mobile Data.
3. Tap Mobile Data.
4. Turn on Allow Mobile Data Switching.

 

[JAYSCS]

1. No matter what, eight signal strength has nothing to do with SIMBA Voice call being dropped because of weak SIMBA signal.

1) Now he is using SIMBA as default for data and voice. SIMBA Voice call will be dropped, if SIMBA signal is weak.

2) Previous case is the same, when SIMBA was set as the default for voice but eight was set as default for data. Again SIMBA Voice call would still use SIMBA 4G connection (VoLTE), not eight 4G connection.

So signal strength of eight does not matter in both cases. eight data connection cannot help for weak SIMBA signal for SIMBA voice call.

2. Why eight signal level drops from 4 bars to 1 bar during the SIMBA voice call is a separate issue. That could mean eight signal is not stable in the same place.

3. In summary: it is better to give up using SIMBA as the main number if he needs more stable network connection for both data and voice call.

So the conclusion could be the user's location is not suitable for using Simba as main line, not Simba being unsuitable as main line, which in any case applies to any other telcos situation due to location connection issue.

 

[xiaofan]

So the conclusion could be the user's location is not suitable for using Simba as main line, not Simba being unsuitable as main line, which in any case applies to any other telcos situation due to location connection issue.

That is just semantics. The fact is that SIMBA is not suitable as the main line for him, a paticular user. Apparently he is bothered by the voice call dropping issues. Another user may not be so bothered by the issue.

He still needs to test other lines, I tend to guess eight 4G is also not suitable for him.

 

[JAYSCS]

That is just semantics. The fact is that SIMBA is not suitable as the main line for him, a paticular user. Apparently he is bothered by the voice call dropping issues. Another user may not be so bothered by the issue.

He still needs to test other lines, I tend to guess eight 4G is also not suitable for him.

Nevertheless, we are guessing what could be the user's underlying problems. I have the feeling that it could be the phone's issue as his situation is very unusual.

 

[gregory_choo]

Different location, and now it's happened again.

I was making a call from my Simba line (primary line), except that this time the data usage is set to Simba (previously Eight).

For record, Simba line shows 2/4 bars on my iPhone while Eight shows 4/4. The latter looks better, right?

While making the call (on speaker so I was able to observe the screen), the Eight line went all the way down to 1/4 bars.

This could highly be the reason why my previous call from the Simba line was cut off, when data usage was set to Eight. Simba calls need VoLTE, right? So when the Eight line went down/off, the call got cut off.

Does that mean I've to 1) use only Simba line for data usage, or 2) port this primary line out to another telco that doesn't need VoLTE for calls, so that I can set data usage to other telco lines as and when I like?

This is what Gemini said:

It sounds like you’re experiencing a common technical "hiccup" found in dual-SIM iPhones. You've actually made a very sharp observation about how VoLTE (Voice over LTE) behaves when your data and voice lines are split.
Here is a breakdown of why this is happening and how to fix it.
Why your calls are dropping
In Singapore, the 3G networks have been phased out. This means all calls now rely on VoLTE. When you use two lines on one iPhone:
* The "Data Hijack": When you make a call on your Simba line, the phone needs a stable LTE connection to maintain the voice data.
* The Conflict: If your data is set to Eight, but you are talking on Simba, the phone is trying to maintain two separate high-speed connections simultaneously. On many iPhones, the secondary line's signal often drops or "shunts" because the antenna is prioritizing the active call.
* The Result: If Eight’s signal drops while it is providing the data for your Simba call, the Simba call loses its "bridge" to the network and cuts off.
Addressing your two options
Option 1: Use Simba for Data (The "Quick Fix")
This is the most stable configuration. When the line you are calling from is also the line providing the data, the iPhone doesn't have to juggle two different network paths for a single task.
* Pros: Immediate stability; no more dropped calls.
* Cons: You might not be able to utilize the "better" signal or higher data quota of your Eight line.
Option 2: Port to a non-VoLTE Telco (The "Myth")
Actually, this isn't really an option anymore. All Singapore telcos (Singtel, StarHub, M1, and MVNOs) now require VoLTE for calls because 3G is gone. Even if you port to a different telco, you will still face the same dual-SIM priority issue if your data and voice lines are different.
The "Hidden" Solution: Cellular Data Switching
Before you port out, try this setting on your iPhone:
* Go to Settings > Cellular > Cellular Data.
* Select your preferred data line (Eight).
* Turn ON "Allow Cellular Data Switching".
How this helps: When you are on a Simba call, the iPhone will automatically (and temporarily) switch the data usage to Simba to ensure the call stays alive. Once you hang up, it will switch back to Eight for your browsing.

 

[xiaofan]

This is what Gemini said:

It sounds like you’re experiencing a common technical "hiccup" found in dual-SIM iPhones. You've actually made a very sharp observation about how VoLTE (Voice over LTE) behaves when your data and voice lines are split.
Here is a breakdown of why this is happening and how to fix it.
Why your calls are dropping
In Singapore, the 3G networks have been phased out. This means all calls now rely on VoLTE. When you use two lines on one iPhone:
* The "Data Hijack": When you make a call on your Simba line, the phone needs a stable LTE connection to maintain the voice data.
* The Conflict: If your data is set to Eight, but you are talking on Simba, the phone is trying to maintain two separate high-speed connections simultaneously. On many iPhones, the secondary line's signal often drops or "shunts" because the antenna is prioritizing the active call.
* The Result: If Eight’s signal drops while it is providing the data for your Simba call, the Simba call loses its "bridge" to the network and cuts off.
Addressing your two options
Option 1: Use Simba for Data (The "Quick Fix")
This is the most stable configuration. When the line you are calling from is also the line providing the data, the iPhone doesn't have to juggle two different network paths for a single task.
* Pros: Immediate stability; no more dropped calls.
* Cons: You might not be able to utilize the "better" signal or higher data quota of your Eight line.
Option 2: Port to a non-VoLTE Telco (The "Myth")
Actually, this isn't really an option anymore. All Singapore telcos (Singtel, StarHub, M1, and MVNOs) now require VoLTE for calls because 3G is gone. Even if you port to a different telco, you will still face the same dual-SIM priority issue if your data and voice lines are different.
The "Hidden" Solution: Cellular Data Switching
Before you port out, try this setting on your iPhone:
* Go to Settings > Cellular > Cellular Data.
* Select your preferred data line (Eight).
* Turn ON "Allow Cellular Data Switching".
How this helps: When you are on a Simba call, the iPhone will automatically (and temporarily) switch the data usage to Simba to ensure the call stays alive. Once you hang up, it will switch back to Eight for your browsing.

1) I have doubts on the solution provided.

I doubt Option 2 will help. I think he has already tested that one. I mentioned that option previously to him.

Option 1 will not help either if SIMBA signal is weak to maintain the VoLTE voice call.

2) But there is one potentially good explanation for the reason why the eight signal drop during the SIMBA voice call. iPhone is not famous for good signal reception in the first place. This may make things worse for the other SIM.

On many iPhones, the secondary line's signal often drops or "shunts" because the antenna is prioritizing the active call.

 

[JAYSCS]

1) I have doubts on the solution provided.

I doubt Option 2 will help. I think he has already tested that one. I mentioned that option previously to him.

Option 1 will not help either if SIMBA signal is weak to maintain the VoLTE voice call.

2) But there is one potentially good explanation for the reason why the eigth signal drop during the SIMBA voice call. iPhone is not famous for good signal reception in the first place. This may make things worse for the other SIM.

On many iPhones, the secondary line's signal often drops or "shunts" because the antenna is prioritizing the active call.

Conclusion: Switch to Android device if dual SIM is s must, else use 2 iPhone for 2 SIMs, anyway iPhone all along has been a single SIM device, it is only eSim introduction that lead to dual SIM function, thus definitely not its strength.

 

[A7997A]

Take note "Allow Mobile Data Switching" does not help here since it is about SIMBA voice being dropped, not the data connection of the iPhone being dropped during the voice call.

https://support.apple.com/en-sg/109317

If you turn on Allow Mobile Data Switching, then while you're on a voice call on your voice-only number, that number will switch to using voice and data automatically.6 This will let you use both voice and data while on the call.

If you turn off Allow Mobile Data Switching and you're active on a voice number that isn't your designated mobile-data number, then mobile data won't work while you're on the call.

To turn on Allow Mobile Data Switching, follow these steps:

1. Go to Settings.
2. Tap either Cellular or Mobile Data.
3. Tap Mobile Data.
4. Turn on Allow Mobile Data Switching.

Unless Backup calling kicks in, but in my experience that doesn't happen as long as you have some sort of Simba connection, even if it is bad. VoWifi can help if one is often at a location with good wifi connection, but doesn't work once you move out of that.

 

[Habrosus]

1) I have doubts on the solution provided.

I doubt Option 2 will help. I think he has already tested that one. I mentioned that option previously to him.

Option 1 will not help either if SIMBA signal is weak to maintain the VoLTE voice call.

2) But there is one potentially good explanation for the reason why the eight signal drop during the SIMBA voice call. iPhone is not famous for good signal reception in the first place. This may make things worse for the other SIM.

On many iPhones, the secondary line's signal often drops or "shunts" because the antenna is prioritizing the active call.

Reason I chose to make Simba my main line coz it works wonderfully when I'm roaming, smooth auto switching so I don't have to worry if my line is dead when family needs to contact me. Local calls not that important save for the occasional bank calls.

I've not really gone to try the "allow data switching" option as I was (still am) on the move quite a bit and won't have many chances to sit down for calls like these.

If it makes any difference, previously was Eight 5G line and today's 4G pending upgrade.

So far the combo of Simba calls and data work is tolerable, working when I need, except for this weird Eight signal incidents...

Conclusion: Switch to Android device if dual SIM is s must, else use 2 iPhone for 2 SIMs, anyway iPhone all along has been a single SIM device, it is only eSim introduction that lead to dual SIM function, thus definitely not its strength.

I started using dual SIM to have easier access to my Malaysian line, was on Android too, until the Samsung Note 9 green screen saga. That's when I switched completely to Apple devices.

And... I'm already not a single phone user. Just that this 17PM is my current primary phone. With eSIM it also lets me play with multiple lines.

Edit : Thanks to everyone for your input, very informative read.

 

[Habrosus]

Does anyone have any official words from their staff that connectivity is prioritized according to plan type?

 

[SBS2716G]

Anyone cancel their Simba line within the first month? Will have $30 activation charge incurred? Their FAQ say so.
But the submit termination request mention only port out will incurred $30 charge.

 

[Habrosus]

Anyone cancel their Simba line within the first month? Will have $30 activation charge incurred? Their FAQ say so.
But the submit termination request mention only port out will incurred $30 charge.

Termination request via online form? Can try by choosing the option "end of cycle".

 

[xiaofan]

Anyone cancel their Simba line within the first month? Will have $30 activation charge incurred? Their FAQ say so.
But the submit termination request mention only port out will incurred $30 charge.

1. Only Port-Out within 30 days will incur a charge of S$30.

Termination should okay. I have done that myself. Take note I signed up at a physical shop (no credit card info required).

https://support.simba.sg/hc/en-us/requests/new?ticket_form_id=12497541316377

2. Indeed the following FAQ says different things compare to the termination request form.
https://support.simba.sg/hc/en-us/a...How-to-terminate-my-mobile-service-with-SIMBA

3. SIMBA will send a confirmation email like the following. You can see no mentioning of termination charges.

We confirm that your mobile number 89xxxxxx has been successfully scheduled for termination at the end of your current billing cycle, on 24-12-2025.

You will receive a confirmation email once the termination has been completed.

4. Later SIMBA will send the official confirmation email like the following.

Your 89xxxxxx has been terminated. You will not be able to access My Account.

We look forward to serving you again.

 

[NickRevenge]

Does anyone know if I buy a prepaid sim, will the validity start from the day I purchase the sim or when I put the sim in the device? I want to use it for travel

 

[xiaofan]

Does anyone know if I buy a prepaid sim, will the validity start from the day I purchase the sim or when I put the sim in the device? I want to use it for travel

I have never used a SIMBA Prepaid SIM, but I tend to believe you have to activate on the spot.

Please correct me if I am wrong for those who have used SIMBA Prepaid SIM.

https://simba.sg/personal-prepaid

To register for a Prepaid SIM, please visit us at Service Centres or Dealers to sign up.

 

[hwsstx]

Does anyone know if I buy a prepaid sim, will the validity start from the day I purchase the sim or when I put the sim in the device? I want to use it for travel

I purchased on 25Dec...I don't calculate so detail but this is from my Invoice.pdf...

Invoice Period 25/12 - 23/01/2026
Activation Date 25/12/2025

Yes I did plug into a phone on the same day as purchased (25Dec) but I suspect the moment you purchased the SIM it is considered activated.

 

[JAYSCS]

Does anyone know if I buy a prepaid sim, will the validity start from the day I purchase the sim or when I put the sim in the device? I want to use it for travel

I have never used a SIMBA Prepaid SIM, but I tend to believe you have to activate on the spot.

Please correct me if I am wrong for those who have used SIMBA Prepaid SIM.

https://simba.sg/personal-prepaid

To register for a Prepaid SIM, please visit us at Service Centres or Dealers to sign up.

The validity period starts upon activation but usually the Service Centre or retail shops will activate the card for you upon purchase. Technically, if you happen to physically collect the card without activation, you may activate the card within 90 days but if you receive the card via post, you need to activate it within 14 days for security reason.