You can use iPhone to make calls in many countries around the world.

Enable international roaming:  
Contact your carrier for information about availability and fees.

Set iPhone to add the correct prefix when dialing from another country:  
In Settings, tap Phone, then turn International Assist on. This lets you make calls to your home country using the numbers in your contacts and favorites, without having to add a prefix or your country code. International Assist works for U.S. telephone numbers only.

When you make a call using International Assist, "International Assist" appears on the iPhone screen, alternating with the "calling ..." message, until your call is connected.

NOTE: International Assist is not available in all areas.