Wrong number registered on my phone

My phone has a phone number registered that is not active. How do I remove it? I changed cell phone companies many months ago and was given a temporary number while they worked on switching over my phone number. When I text or facetime the temporary number shows up. I have called the company and they can not seem to fix it. Today I noticed that the number is on my phone as my number and I think this is causing the problem how do I change this on my phone?