Can l use a at&t iphone 3g with t mobile?

Can l use a at&t iphone 3g with t mobile?

Well that depends on if T- MOBILE has a is run by a sim card.
i know for a fact that AT&T has a sim card slot. But i don't know if t- mobile does.
all you have to do is call them up.
if they do have iphones with sim card slots, all you have to do is take out your AT&T sim card, and insert a t- mobile one.
if they DON't have a sim card slot, then you would have to call up t- mobile and ask them if they can transfer you, or go to the nearest store.
if they can't, th best thing i would recommend to do is sell you AT&T one and use the money to buy a T- MOBILE.