Not sure if you guys know or not, but i see in oversea forum that iphone 4 connect to the internet even if turn the roaming or cellular data off. It especially happen in the early morning. It say it maybe due to problem with the iOS.

For those who have their iphone, could try this exp and report back here.

Reset your iphone data usage to zero b4 going to bed. When wake up the next morning, check the date usage if it goes up.
You also can cehk with cs what is your data usage or total bill today and the next day check with them again, if there any excessive data charge.

I think about to get ip4 but had to hold back due to this problem (more serious than the antennagate issue as there have reported bill more than USD1000 as it get high especially if the user goes overseas and incur mobile international roaming).