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You can turn off your own caller identification, your number will then not be shown at the receiving end when you make a call. Your number is only hidden when you make voice calls not when you send messages.
Find "Show My Caller ID"
Press Show My Caller ID.
Turn your own caller identification on or off
Press the indicator next to "Show My Caller ID" to turn the function on or off.
Return to the home screen
Press the Home key to return to the home screen.