Last month, T-Mobile confirmed that it will support iOS 8's new Wi-Fi calling feature when the update officially launches this fall. And today, the feature went live for developers with T-Mobile iPhones in the just-released iOS 8 beta 3.
For those unfamiliar with Wi-Fi calling, it allows users to place phone calls [natively] from their device over a Wi-Fi network, instead of their cellular network. Benefits of the feature include better call quality and improved battery life...