I was a little nervous about taking my iPhone to Canada as I’d heard horror stories of rampant international data usage leading to $3,000 phone bills. It turned out to be no trouble at all to make sure the phone wouldn’t go nuts overseas. First, AT&T has this page of tips which essentially boil down to:
- Turn off the General → Network → Data Roaming setting. (Which was already set to off when I checked it on my phone.)
- Change the Mail → Auto-Check setting to “Manual”.
- Use Wi-Fi networks whenever you need to access data.
The first one is the most critical as otherwise the phone will use any cell network it can find to send and receive data.
One thing these steps don’t protect you against is voice and SMS usage. I didn’t use the phone but I sent a few SMS messages which cost 20¢ per message.