A simple statement for you: unless you have AT&T stock, don't take your iPhone with you when you go abroad. If, for some crazy reason you decide you moost haf eet, at least do yourself a favor and:
- disable data roaming
- disable 3G
You may also want to enable Airplane mode, just to be sure.
I say the above after having returned from two weeks in Ireland. Before we left we signed up for the 20mb international data plan and international roaming. What we didn't do was: