See info on this SIMBA (TPG) Web page with regards to calls & SMS while overseas:
https://support.simba.sg/hc/en-us/articles/4487047558681-Does-roaming-cover-calls-and-SMS-
From the above. my understanding is that:
If
your phone supports native VoLTE calls on the SIMBA (TPG) network when in Singapore --
then the same phone should also be able to make/receive VoLTE calls when overseas --
provided the following 2 conditions are met:
+ You must connect to the correct SIMBA (TPG) partner telco when overseas.
+ The overseas SIMBA (TPG) partner telco must also support VoLTE calls on their network.
For the list of SIMBA (TPG) overseas partner telcos, see this link:
https://support.simba.sg/hc/en-us/a...l-partner-network-operator-s-per-destination-
In Singapore, if your phone don't support native VoLTE calls on the SIMBA (TPG) network -- then (of course) you can use the
TPG 4G voice app for making/receiving calls.
The TPG 4G voice app can also be used overseas but only in these destinations:
Malaysia, Indonesia, Thailand, Philippines, India, Japan and Taiwan