Phone number?

I changed my phone number through my phone company.. Boost Mobile.. months ago. I sign into my online Boost account with the new number. However in my settings on my iPhone it still has the old number listed as my FaceTime & iMessage number. The only way to change it is to send a verification code to my old number... But I don’t get texts or calls to that number anymore. Someone else has it now. I added my new number but it doesn’t have the option to make it my FaceTime & iMessage number. I don’t know what I’m supposed to do and I need help!