[wizkids0]

Hello everyone I'm a current 810 user on the T-mobile network and seen an ad on Craigslist for a 1520 and am interested in buying it but since its a At&t phone does it need to be unlocked to work with my sim and to pick up T-Mobiles LTE network?

[Silviu Bogusevschi]

Greetings!

Not sure about LTE, but you definitely need to unlock it in order to use a SIM from a different carrier.

[wizkids0]

Even though they run off a GSM network it would still need to be unlocked? I once had a 822 and when I put a tmobile sim in it ran off 3g and got cell service but wouldn't allow me to send SMS messages but could call and everything else

[RumoredNow]

If it is an AT&T branded phone, it needs to be unlocked in order to use a T-Mo SIM.

It does not have the right 3G radio for T-Mo if you are in a refarmed area that has LTE so EDGE only when LTE Band 4 is not available.