The carrier has switched on VoLTE (aka HD Voice) in both the District of Columbia as well as certain areas in 13 other states, ranging from Washington to Texas. The company isn't saying just which cities are getting the improved service, but it's a big step forward for a fledgling technology -- if you subscribe to AT&T, you're now that much more likely to have a pristine-sounding conversation. Now if only American providers could get their LTE calls crossing networks.
