Show my phone number when I call someone

This depends on your Cell carrier— if you are having issue contact their support.

ref: https://discussions.apple.com/thread/250074727?answerId=250132737022#250132737022

Your iPhone should do just that by default. If it is not doing that and others are not seeing your phone number when you call them then Go To Settings-->>Phone-->>Show my Caller ID and ensure that it is set to ON.

Good Luck.

Axel F.