Wifi calling on the G2 is UMA based, AFAIK. Even works with your existing router, unlike the earlier T-Mo stuff where they wanted you to buy their router to do

Wifi calling on the G2 is UMA based, AFAIK. Even works with your existing router, unlike the earlier T-Mo stuff where they wanted you to buy their router to do it. They've dropped the extra monthly charge for using it, as well, though it does still use plan minutes. Sound quality is a little worse than 3G calling, IME, but it works very well. It's been handy in my office where T-Mo signal is a little spotty. (Yet, I step outside the front door and have 5 bars ;)).