How to remove an old phone number

Hi,

I have since purchased a new SIM for my iPhone & transferred my old number to my new Sim. Once the number had transferred & I started using my phone, my friends were telling me that when I FaceTime them, it’s not my number coming up. In my settings the number that came with my new sim is still registered for Facetime and iMessage along with my old number I kept. But I cannot deregister the new number as the only options are, put the SIM card back in of the number you want to de register and to switch off the setting or send a code to that number to type in. I can’t do either.

help