Took me 7 minutes to get my code, i'm also on AT&T.
You have nothing to worry about bud, .
Yeah, just make sure that you get AT&T or T-Mobile.
Verizon - Costs in-between Sprint and AT&T because it's pre-unlocked, but the service can be iffy.
Sprint - Just complete ****e. You can't use other SIMs and expect to have good service.
AT&T and T-Mobile, for example, are $450 on Ebay. Verizon are ~$350-$400 and Sprint have gone anywhere from $250-$350 that I've seen.