Wi-Fi calling comes to the AT&T Samsung Galaxy S7 and Galaxy S7 edge
If you can't wait for the notification to appear on your phone telling you that the OTA update has arrived, you can check it out manually. Go to System > About device > Software update > Check for updates. So let's say that the update has arrived. Before you start the process of downloading and installing it, make sure that you are connected to a Wi-Fi network. And you should also make sure that your battery is fully charged before going ahead with the update.
Besides adding Wi-Fi calling to the handsets, the update comes with the July security update, changes to Setup and Transfer, and the inclusion of AT&T's advanced messaging system (IPME).