AT&T offers phone-free SIM card
Buy a SIM card from AT&T and use your own cell phone.
The 3G, 64K SIMs are just $10, but you get a whopping $5 discount if you sign a two-year contract (hint: sometimes it's best to pay full price). Alternatively, if you don't fancy contracts, you also can use the cards with the carrier's GoPhone prepaid service. Though the rumor mill is saying that the phone-free SIM cards don't entitle you to multimedia messaging, I'd be surprised if that was the case, and AT&T doesn't list any such restrictions on its Web site. The carrier only says you must use the SIM card with an unlocked or locked AT&T cell phone that operates on the 800 to 900 GSM bands. Also, the handset should not have been previously reported as lost or stolen. So go ahead, free your phone!