I am currently commuting between Germany and South Africa. I have started testing VO-WiFi as a means to stay connected and have a local presence in both countries without the high roaming fees.
Preconditions for VO-WiFi are VO-LTE/VO-WiFi support by the service provider and the phone. Typically VO-WiFi calls are seen as originating in the country where you have the service. They are therefore charged as local calls according to the plan you are on.
I have tested VO-WiFi using a German O2 SIM. Call quality is great on my home WiFi which is powered by a Telkom mobile SIM. Incoming calls to my German number are also possible. Calls use my call plan on Germany.
To connect on the move in I can of course has a second phone providing a hotspot. What I would like to do is use a dual SIM phone where one SIM can provide local data and the other WiFi calling. This is reported working pin the new iPhones but had anyone tested this on an Android device?
Many of today's dual SIM phones do allow LTE functionality on both SIMs. This would be required. The older dual SIM phones only support data on one SIM and only VOWiFi on the same SIM.
Secondly which S.A. providers support VOLTE/ VOWiFi?