How do you unlock the AT&T S3 for use on TMobile?

JEGuitarist

Member
Sep 9, 2012
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My girlfriend is giving me her old S3 since she just upgraded to the new model, but I don't want to use AT&T, I'd like to switch to the Tmobile $30 a month plan. How do I go about unlocking the phone so I can switch? I've read a lot about unlock codes, and a lot of different ways to go about it..just not sure where to start.

Thanks
-JEGuitarist