T-Mobile has offered this service for years now with other phones, but with iOS 8, it has confirmed that it will indeed support this feature. Sprint also has support for Wi-Fi calling but has not announced if they will support iOS 8's feature. However, AT&T and Verizon have yet to rollout this service.
With Wi-FI calling, there is no activation or app required, you simply connect to your home wireless network and make/receive calls or texts like your normally would.
Like HD Voice, Voice-over LTE (VoLTE) and a host of other pioneering wireless innovations, T-Mobile has also long led the way with Wi-Fi Calling. Back in 2007, we were the very first US wireless provider to enable Wi-Fi Calling nationwide on our Android-powered and Windows smartphone
Now -- with the news coming out of Apple’s keynote today that Wi-Fi Calling will be enabled with iOS 8 – I’m excited to welcome our iPhone customers to the convenience and ease of T-Mobile Wi-Fi Calling as well.
One of the best things about T-Mobile Wi-Fi Calling is that it’s so simple to use. You don’t need to activate anything or download a special app. Just connect to any available Wi-Fi network, check that Wi-Fi Calling is turned on on your capable smartphone, and make a call (or send a text, email, etc.) as you normally would. That’s it.
T-Mobile currently carries over 30 HD Voice-capable devices and – to date – T-Mobile customers have made over 5 billion HD Voice calls and have enjoyed over 12 billion minutes of HD Voice since launch.
T-Mobile also launched Voice over LTE in Seattle, with plans to expand it soon across the nation. VoLTE routes all calls over the LTE network instead of the 3G network, providing crystal-clear quality.