Long story short, I'm looking at purchasing a phone that the seller says is unlocked and I'm wanting to use it on TMobile. How do I confirm that the ESN is clean? Do I need to contact ATT (where I think the phone is from) or T-Mobile (where my brother wants to activate it) to confirm this? I don't want to buy a phone and find out it's stolen. I've always dealt with CDMA phones so I have no idea where to go with this. Edit: Also, is there any way I can confirm the phone is indeed unlocked?