Step Determine the 'Calling Frequencies' for your T-Mobile Phone. The available frequencies are currently 850mhz, 900mhz, 1800mhz, and 1900mhz. T-Mobile operates on the 1900mhz frequency, but many of their phones offer 2, 3 and even all four of these frequencies. In order to operate via AT&T your device will require the 850Mhz AT&T frequency. You can find your devices available calling frequencies in the phone's user manual or typically on the original retail box. If you do not have your manual or box, GSMArena is the authoritative voice for GSM specifications.
T-Mobile customers can unlock their devices by calling. Shop Iphone 6 Plus Unlocked more. T-Mobile’s website says that a customer can ask for two unlocks per line per year.
Step Determine how long you have been a T-Mobile customer. If your contract is at least 121 days, T-Mobile will typically provide you with your 'unlock code' for free. Find Out If An Iphone Is Unlocked. If you have not had your phone on your current contract for at least 121 days, T-Mobile will not provide the unlock code. Iphone 5 Passcode Password Bypass Unlock.
Simply call T-Mobile customer service at 1-800-Tmobile and request your device's unlock code. Type in the code exactly as provided to you by the customer service representative. Unlock Tmobile Phone For At&t.
After entering the code, reset your device if it doesn't do so by itself and then insert your AT&T Sim card--you should now receive a signal. Step The unlock code will usually involve typing a set of numbers with several of the device's other keys included in the process. For example, holding down the two soft keys on your phone while typing '#1293_' and then a code such as '_1234.'