You're not supposed to do be able to do so. That doesn't stop people. Alternatively, you can take the risk and try deactivating it within 30 days, which by contract won't get the early deactivation keys... but good luck dealing with AT&T right now.

I personally wouldn't see the point in paying 500 or 600 USD for an 8gig portable media player, particularly with Archos coming out with the 5th gen models soon, but whatever works for you.