This article explains how to make calls using a Wi-Fi network instead of your phone's network on a Samsung S5 or later. You may also be able to enable Wi-Fi calling on other Android phones.
How to Enable WiFi Calling on Samsung
You can use a couple of methods to enable Wi-Fi calling. The first is in your phone’s settings app.
Make sure you are connected to a Wi-Fi network.
Open your phone's Settings and tap Connections.
