A free program for Android, by MV Infotech LLP.

The app WIFI Voice Calls allows users to make voice calls while connected to WiFi. The app enables users to access settings where they can activate the WIFI Calling function, which enable them to make free phone calls over the internet utilizing WiFi and without any carrier fees, such as per-minute charges. That could entail connecting to a Wi-Fi network you have set up at home or using whichever Wi-Fi hotspot you chance to be using when you are out and about, like as a restaurant or university. You still use standard phone numbers, and it works largely the same as any other phone call.