Bro, wifi calling is network based feature, only jio and airtel are in advanced phase and very soon they both will come up with this feature..
If you don’t have a cellular signal or it’s spotty, the ability to make WiFi calls comes in handy.
Instead of using your carrier's network connection, your phone can make a voice call via a Wi-Fi network. This is the same Wi-Fi connection you have set up at home, or whatever Wi-Fi hotspot you happen to be on when you're out and about, such as at a cafe or library. In most ways, it's like any other phone call, and you still use regular phone numbers.
Wi-Fi calling is especially useful when you're in an area with weak carrier coverage. For example, when you're traveling to the residential countryside, or you're in a building with spotty reception
