I have a 64 GB iPhone 5 that I got on launch day in 2012. Originally on AT&T and I got it unlocked by AT&T (ran the restore on iTunes and got the confirmation). I just switched to T-Mobile. The SIM works fine in it, but the speeds are often slower and on Edge. After some research, it looks like they made a change to the iPhone 5 in March 2013 to have the internal radio support the T-Mobile bands. The phone is still the A1428 model number, but in the phone About screen it says model MD642LL/A. It looks like the newer versions of this same phone from 2013 all start with a ME prefix instead of MD. If I take this phone to my local Genius Bar, do you think they would swap it out for the newer version? I do have AppleCare+ and don't want the phone to have an "accident" to take it in for such a replacement. Curious if other have encountered this issue and if you were able to resolve it at a Genius Bar. Thanks!