I purchased (3) T-Mobile iPhone 5-S's thru Apple web-site and paid in full at time of order so I will assume they are NOT locked. I ported over our numbers from Verizon upon initial registration at T-Mo and I've been relatively happy with their service, however, while traveling the T-Mo coverage is just not there. My wife is a flight attendant and has noticed the degradation in cell coverage wherever she travels. QUESTION: Is the T-Mobile specific iPhone 5-S hardware and the frequencies used compatible with AT&T? Can I just swap out the SIM's and port numbers over to AT&T service? Or would I be better off to sell these and buy new AT&T specific iPhone 5-S's. I will never return to VW. Thanks to all the respond.