Apple iPhone iOS 8.1 - Manual (Page 54)

Chapter 5 Phone 54
Go to Settings, turn on Airplane Mode, then tap Wi-Fi and turn it on.
Make calls to your contacts and favorites while traveling abroad. (GSM) Go to Settings > Phone
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.
Phone settings
Go to Settings > Phone to:
See the phone number for your iPhone
Change the default text message replies for incoming calls
Change your voicemail password (GSM)
Require a PIN to unlock your SIM when you turn iPhone on (required by some carriers)
Go to Settings > Sounds to:
Set ringtones and volume
Set vibration options
Set the sound for new voicemail