SingTel

[Caelitus]

In Singtel's case, I thnk voice-over-WiFi is part of the heterogeneous network where traffic can be seamlessly routed between Wifi and mobile networks to optimise the bandwidth. That is to say, if you are currently on a voice call (mobile network) and you step into a area with weak mobile network coverage but stronger WiFi coverage, the system hands over the call to the cell with the stronger coverage. I presume if you are on a Whatsapp call, once the data network signal gets cut off or you are handed over to a non-data network, your call is terminated.

I am using 3 mobile 4G plan here in the UK. This company has an app that allows me to receive calls/sms over a WiFi network where the mobile coverage is very weak or non-existent. Minutes/text messages are deducted from my allowances if made over the WiFi network. To my knowledge, they do not have a het network where I can transit seamlessly between the two.

<Vested in Singtel because one of the reasons is that I have a Singtel subscription and I want to collect money back from them lol>