AT&T uses GSM and as such they are issues and switching from a CDMA system. The following might help you: –
AT&T phones
- GSM carrier
- Phones should be compatible with T-Mobile Network
- Phones can't be used on Sprint and Verizon networks (unless global)
- 2G: 850MHz and 1900MHz frequencies
- 3G: 850MHz and 1900MHz frequencies
- 4G (LTE): 700Mhz (bands 17 and 29), 850MHz (band 5), 1700 MHz (band 4), 1900MHz (band 2) and 2100MHz (band 4)
AT&T uses a GSM network, meaning its phones all come with a SIM card. In theory, you should be able to take your AT&T-branded device to fellow GSM network T-Mobile. For the most part this holds true, although there is the odd exception - so be mindful.
Note that T-Mobile and AT&T operate over different frequencies. Some of them overlap, but not all. This means that, while your phone may ‘work’ when going from one to another, you may suffer diminished reception, as your device may not be compatible with all the frequencies utilized by whichever network you have switched to.
Phones sold through AT&T are locked to its network. You can request an unlock code, but you need to fit the criteria:
- It must be paid off in full, and not still on contract or a payment plan
- It is not currently active on a different AT&T customer’s account
- If you performed an early-upgrade, you must wait a 14 day ‘buyer’s remorse period’ before you can request an unlock to your previous device
- It must not be associated with fraudulent activity, reported lost, or reported stolen
- Post-paid customers must have an account that has been active for at least 60 days, with no past due or unpaid balance
- Prepaid devices must have been active for at least six months of paid service
AT&T reserves the right to amend this unlocking policy at any time without advance notice.
.
(data not working)...
