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Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0_1 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A400 Safari/528.16)

Yes, if it's unlocked it should work by just inserting your sim card
 
Thank you, Nine9si.

Aside from applications, will iTunes then allow me to sync music, videos, etc., or will it still ask to set up the iPhone?
 
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0_1 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A400 Safari/528.16)

You can sync anything you would with a normal iPhone on AT&T.
 
Success... I think :)

SIM card worked, seemed to have phone service, but didn't recognize the data plan that's on the T-Mobile account, and contacts were missing (maybe this intentional?). Also, neither the iPhone or iTunes displayed the phone number. Do I need to do something special for that?
 
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