The company introduced the feature for iOS devices last October, and starting today you can make calls and send and receive texts over Wi-Fi so long as you own LG's 2015 flagship and install the requisite software update. AT&T says it plans to add more Android devices soon. The feature works by detecting when you're in an area with limited cell coverage and connected to a Wi-Fi network. From there, you can use your phone for calls and texts just as you would normally.
Wi-Fi calling has a few other limitations right now. It only works for AT&T customers in the US, Puerto Rico, the Virgin Islands, and select international countries. If you call a domestic number over Wi-Fi, you won't incur any charges. But you will have to pay standard international rates if you call an international number. You also need to have a post-paid wireless account, so pay-as-you-go customers are out of luck.