Upgrade iPhone

I have been with Xfinity for 12 years and pay what i can I’m a Diamond member. So i need a new iPhone my iPhone is iPhone 12 ) got texts saying I’m eligible to upgrade iPhone to iPhone 18 because I have been with them for 12 years, received a call saying you can get a one year free with Xfinity Mobile service they sign me up for Now Mobile they got my credit card number and started billing me waiting i have free service now mobile will not take my credit card off their account and will not take credit card off their computer taking money off credit card wait i have free mobile service from Xfinity free one year. Now Mobile refuses to take credit card off their computer because XFinity made a mistake Now Mobile is taking money off credit card will not remove it. Now I can upgrade my iPhone and they will not give it to me because I was not paying for service it was free one year September it expired they said I can’t upgrade my iPhone because I was not paid for service,. Got text message for iPhone 18 on them and they will not give me it not fair 😱😫Why 12 years been with them should I leave find new cell phone company?