Wi-Fi calling coming to AT&T in 2015
Last week, T-Mobile said that 100% of phones sold by the carrier will now include the feature. T-Mobile gets a head start on AT&T as de la Vega said that the mobile operator would not launch the new service until it was thoroughly tested, which points to a 2015 launch. AT&T will offer VoWiFi with seamless handoff in place, similar to T-Mobile's version. The AT&T executive sees Wi-Fi calling complementing its current voice options like VoLTE and 3G Voice. The announcement was made at the Goldman Sachs Communacopia Conference.
Sprint has offered Wi-Fi calling, although its service is limited to a few Android models. Other carriers like Republic Wireless have their customers make calls over Wi-Fi where possible, using Sprint's cellular network to fill out gaps where there is no Wi-Fi available.
source: LightReading via TechCrunch