Method 1:
The first method that you can use to hide your phone number is to simply add #31# before the number you are dialing. This should be done each time you are attempting to make a call. For example if you want to dial someone's number but you don't want to reveal your number or identity via through Tru caller simple dial the number using this format #31#09030055417 -- --- You should also note that whenever you remove #31# that is in front of the number,your number automatically becomes visible. This method works for all mobile phone network in Nigeria i.e MTN,Glo,Airtel & 9mobile
Method 2:
The second method is also quite easy,depending on the type of mobile phone you are using,you can easily hide your number,most often this functionality is found in ''Phone Settings. All you should do is to follow the easy steps: Go to Settings > Call Settings > Show/Hide Caller ID You can then toggle the settings on or off,to either reveal or hide your number. If you have any questions,you can ask in the comments section below.
Source: How To Hide Number On MTN,Glo,Airtel & 9mobile In Nigeria