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.
Slide your finger downwards starting from the top of the screen.
Tap the settings icon.
Tap Additional settings.
Tap Caller ID.
Tap Show number to turn on caller identification.
Tap Hide number to turn off caller identification.