The iPhone is a quad-band GSM phone, which is a fancy way of saying it also works in any of the 200 countries of the world (including all of Europe) that have GSM phone networks. Cool!
But AT&T's international roaming charges will cost you anywhere from 60 cents to $5 per minute. Not so cool!
If you, a person in Oprah's tax bracket, are fine with that, then all you have to do is remember to call AT&T before you travel. Ask that they turn on the international roaming feature. (They can do that remotely. It's a security step.)
Then off you go. Now you can dial local numbers in the countries you visit, and receive calls from the U.S. from people who dial your regular number, with the greatest of ease. You can even specify which overseas cell carrier you want to carry your calls, since there may be more than one that's made roaming agreements with AT&T.
See Carrier for details on specifying the overseas carrier. And see www.wireless.att.com/learn/international/long-distance for details on this roaming stuff. (Beware of the data charges—they're even higher than the voice charges. Bills of $4,000 aren't unusual following three-week trips abroad! See Phone.)
If you're not interested in paying those massive roaming charges, however, you might want to consider simply renting a cellphone when you get to the country you're visiting.
Note
The iPhone can even add the proper country codes automatically when you dial U.S. numbers; see Phone.
As for calling overseas numbers from the U.S., the scheme is simple:
North America (Canada, Puerto Rico, Caribbean). Dial 1, the area code, and the number, just like any other long-distance call.
Other countries. Dial 011, the country code, the city or area code, and the local number. How do you know the country code? Let Google be your friend.
Tip
Instead of dialing 011, you can just hold down the 0 key. That produces the + symbol, which means 011 to the AT&T switchboard.
These calls, too, will cost you. If you do much overseas calling, therefore, consider cutting the overseas-calling rates down to the bone by using Jajah.com. It's a Web service that cleverly uses the Internet to conduct your call—for 3 cents a minute to most countries, vs. 11 cents using the phone company.
You don't have to sign up for anything. Just go to www.jajah.com on your iPhone. Fill in your phone number and your overseas friend's, and then click Call.
In a moment, your phone will ring—and you'll hear your friend saying hello. Neither of you actually placed the call—Jajah called both of you and connected the calls—so you save all kinds of money. Happy chatting!