I've noticed recently that when you place a call, the phone immediately goes from LTE to 4G. The data connection is barely usable while on a call, which defeats the sales marketing that AT&T uses against its competitors. I've validated the issue on multiple iPhone5's on AT&T network. I've also validated this on version 6.0.1 & 6.1.2 with the same results. Not sure if this is an AT&T issue or Apple, however should be addressed.