Since your query has been answered, just adding on to some FYI
Seller advised to activate eSIM line and Data roaming when I reached HK
Activating purchased roaming esim first locally few hours before your flight and activating data roaming is a common procedure though some seller would "prefer" or "need" you to activate once you reach your destination.
In the latter case, you would have to find free airport wifi to do that...... so most people don't do that unless you are travelling in group and can "borrow" wifi. Unless of course, it is a requirement by the seller, this does exist.
Turn off my Singtel primary line.
Seller care about you as you might incur roaming cost, and they probably receive alot of complain "why didn't you tell me to disable" from other first timers
Some people do leave it on mostly due to expected SMS authenication or they have IDD / roaming data that they can use. If you are not sure, either ask your telco or just simply disable it if you are not expecting any SMS or CALL
) first disable Roaming in my Singtel App (ie my SIngtel SIM card is unable to roam)
Maybe ask this in the SINGTEL SIM ONLY or related singtel threads, they would be able to advise you on this.
2) in iPhone settings, just leave my Singtel primary line on and eSIM secondary line on? Since Singtel "Roaming" is disabled, my phone will auto use the eSIM line for roaming?
Android user here, not sure about iphone.
In any dual sim (with esim support) phone, you can tell it to use which sim card to use for
- Call
- Data
If the option is missing to switch is not available, it might need to detect 2 sims first.
For my case, my telco is EIGHT. Since i have free incoming SMS and global roaming data, i just leave it on.
Then i just change the "DATA" or "INTERNET" to the esim that i have installed and activated once i land