Apple iPhone OS 3.1 - Manual (Page 58)

Important: If Data Roaming is turned on, you may incur charges when roaming
outside your carrier’s network for the use of any of the features listed above, as well as
for delivery of visual voicemail. Check with your carrier for information about roaming
charges.
Get voicemail when visual voicemail isn’t available: Dial your own number, or touch
and hold “1” on the keypad.
You can use Airplane Mode to turn off cellular services and then turn Wi-Fi on to get
access to the Internet, while preventing voice roaming charges.
Use Airplane Mode to turn off cellular services: In Settings, tap Airplane Mode to turn
it on, then tap Wi-Fi and turn Wi-Fi on. See “Airplane Mode” on page 138.
Incoming phone calls are sent to voicemail. To make and receive calls again and get
your voicemail messages, turn Airplane Mode off.
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