Hey- I was in the U.S. last year with my unlocked and jailbroken 3GS, and for awhile, I had no problem with a pre-paid ATT card – and they also had a data plan which was not so expensive. But then, the Edge started not working, so I just used it with the Wi-Fi at home and in Starbucks, and cafes, etc. so, then I switched to a T-Mobile pre-paid but with no data plan – but there were no limited features, otherwise. another thing – where I live now, a disadvantage of the iPhone is that you get charged for Internet even though EDGE is turned off and you dont even have a data plan. I had to download BossPrefs from Cydia to toggle it off. then BossPrefs was superseded by SBSettings – but I still could not toggle off Edge – so I went back to BossPrefs. it must be a common problem or they wouldn’t have these programs. where I live now there are cheap data plans for pre-pays, but you have to monitor your Internet usage so you don’t go over the package limit or the price goes way up. anyway, check out SBSettings – there’s a ton of cool things you can configure your jailbroken iPhone with that program. Also, in the links below there is a discussion on how they have fixed the toggle data off in SBSettings.