What is Wi-Fi Calling? How to Enable it on iPhones, Android Smartphones

W-Fi calling enables users to make regular calls in low or bad connectivity areas with the help of Wi-Fi networks. This service only works if your telecom operator supports Wi-Fi calling and the subscriber has a strong Wi-Fi connection. When the network connectivity is low, compatible phones will use the Wi-Fi network to make regular calls through the telecom operator it is subscribed to. In India, most telecom operators offer Wi-Fi calling support, including Airtel, Reliance Jio, and Vodafone Idea. The telecom operators levy no additional cost for this service.   

The new Wi-Fi calling service is especially beneficial in low network connectivity areas. If Wi-Fi calling is enabled on the smartphone, it will use the connected Wi-Fi network to make regular voice calls. For instance, if you’re in the basement of a building and have low network connectivity, but strong Wi-Fi, you will still be able to make seamless regular voice calls. This service looks to improve call quality and reduce call drops. Wi-Fi calling service makes calls over the VoIP (voice over Internet protocol) instead of the VoLTE (voice over LTE) network.  

source: https://gadgets.ndtv.com/how-to/news/what-is-wifi-calling-how-to-enable-android-iphone-smartphone-jio-airtel-vi-vodafone-idea-2559289