It’s no secret that wireless carriers want the iPhone on their networks, and until last year if you wanted an iPhone in the U.S., AT&T was your only official choice.
However 2011 brought us the CDMA iPhone 4 for Verizon, and later on the iPhone 4S was released with full support for GSM along with CDMA, allowing carriers like Sprint to begin offering the device as well.
But T-Mobile USA has yet to bring the iPhone to their network in any official capacity, in part because their 3G network uses a different radio frequency band than AT&T and the rest of the world, one that current iPhone hardware does not support.
Unlocked iPhone owners will be quite familiar with this limitation, as unlocked devices built for AT&T’s network will fall back to 2G EDGE service when used with a T-Mobile USA sim card. Read more