I was in bahamas 5 weekend days end of august, and checked email a couple of times a day, but left the iphone in the safe, due to lots of water sports with my kids. Dialed out 2 times to US. Got $470 data bill.
I was using my blackjack 5 week days in europe in June, checked email all day every day - sent emails, texts, and power used all during the trip. The bill was $175.
The Iphone uses too much data transfer, then does not even hold the emails resident on the handset, as they usually say - email data not downloaded when you go to read the email. You can see the header, but not the email. For all this data transfer not to see the data, then get a bill that is a whopper, Something is not right.

I have yet to receive a credit from AT&T.