you can add a feature called Cingular World by calling customer service.
It is 5.99 a month when you are traveling out of the country.
It is 3.99 when you are in the U.S. calling out of the country.
The feature can be added and removed at any time and is pro-rated.
How it charges: Adding Cingular World reduces your per minute rate, but is still not cheap. You have to talk to customer service to get the specific rates for the country you will be in (or be calling). Before trying to do this you have to talk to customer service for a very important reason, to get your phone unlocked. If you have the iPhone, FAT CHANCE. If you are a new AT&T customer, haha. Usually you have to be an AT&T customer for 6 months first and I highly doubt they'll consider doing it with any iPhone for any reason.