This app has just been released. This app works in the same pricincple as MyRepublic talk app. There are a few other functions like forwarding etc.
The most important feature is that non VoLTE capable Android users will now be able to make calls and receive calls via the app so long there is internet connectivity. Do give it a try and comment below your expeience.
You can download the app for Apple or Android at the link below.
1. Where can I download TPG 4G Voice app?