Won’t let me get new phone with phone paid off

So I’ve been with xfinity for a couple years. I have the wick and 4 mo again I decided to bring 11 pro max over and get cell service! Mistake!  When I try to upgrade or get a new phone (which it says I’m eligible) it then goes to saying I have too many lines r something!  I only have the one!  So frustrating! Guess I’ll switch to another provider now!!!!