For information about making international calls from your home area (including rates and other charges that may apply), contact your carrier.
When traveling abroad, you may be able to use iPhone to make calls, send and receive text messages, and use apps that access the Internet, depending on available networks.
Enable international roaming. Contact your carrier for information about availability and fees.
You may be able to roam on GSM networks, if you have a CDMA account and you have an iPhone 4s or later with a SIM card installed. While roaming on a GSM network, iPhone has access to GSM network features. Charges may apply. Contact your carrier for more information.
Set network options. Go to Settings > Cellular to:
Turn off cellular services. Go to Settings, turn on Airplane Mode, then tap Wi-Fi and turn it on. Incoming phone calls are sent to voicemail. To resume cellular service, turn Airplane Mode off.
Make calls to your contacts and favorites while traveling abroad. (GSM) Go to Settings > Phone and turn on Dial Assist. Dial Assist automatically adds the prefix or country code for calls to the U.S.
Select a carrier network. Go to Settings > Carrier. This setting appears on GSM networks when you're outside your carrier's network, and other local carrier data networks are available to use for your phone calls, visual voicemail, and cellular network Internet connections. You can make calls only on carriers that have a roaming agreement with your carrier. Additional fees may apply. Roaming charges may be billed to you by the other carrier, through your carrier.
Get voicemail when visual voicemail isn't available. Dial your own number (with CDMA, add # after your number), or touch and hold "1" on the numeric keypad.