Can I display/hide my phone number?
To hide your phone number permanently for all calls, you must activate the secret number option via mon.scarlet. It will be activated within 24 hours. After activating this option, call *31# to hide your number. To deactivate this option, simply call #31#.
To temporarily hide your phone number for a call, type *31*phone number# on your handset. You replace the phone number with the number of the person you are calling.