I got a new phone number and I can't change my iMessage phone number
okay so Recently I changed carriers and when I changed carriers I got a new phone number. When I go into the Settings>Messages>Send&Recieve I see my old phone number greyed out and I cant change it. I made a new iTunes account because I thought mahbe the phone number was tied to my iTunes account, didn't work. I reset my network settings, didn't work. Did almost everything on the internet that I could think of and can't fix it. All my messages go through SMS istead of iMessage. I'm using an iPhone 6 (Not Plus).
iPhone 6, iOS 8.1