Xfinity unable to move mobile line

I had 3 mobile lines attached to my original Xfinity account where I also previously received Wi-Fi services, and then after 2 moves, ended up with just the mobile lines on my old account and Wi-Fi services associated with my current address on a new account. I have been DESPERATELY trying to get my mobile service moved to my newer account with my current address and WiFi service. I have spent OVER SIX HOURS on the phone with Xfinity in the last 1.5 weeks, and attempted to go in to a physical store (they said they couldn't help me) and my issue still has not been resolved. They moved 2 of the 3 lines, and every time I call to figure out the 3rd one, they say they've fixed it/put in the request for the fix, and then nothing changes. The longer this 3rd line stays on a separate account, the higher my bill/s are going to be, and I am furious with Xfinity's incompetence on the matter. They keep telling me they're getting an error when they try to process the transfer, but that no one seems to know what the error is or why it's there. After a little bit of Google searching, I *think* I might know what the issue is, and of course, it's a direct result of another big mistake that Xfinity made and only recently "fixed". This being a situation where almost 2 years ago when I last upgraded my phone, Xfinity ordered the wrong phone, which wasn't noticed until it had been shipped out. I received the phone in the mail and returned it according to their directions without even opening the box, let alone powering on the phone. (Though my e-sim magically ported to the new phone while I was out of state, and to "temporarily" fix the issue, they had to issue a new e-sim to my preexisting phone, so I could regain service until I returned home). They then continued charging me for this phone up until 2 weeks ago when they FINALLY fixed it (after me making countless phone calls and store trips to resolve the matter, only for them to repeatedly basically accuse me of never actually returning the phone). That "wrong" phone still appears on my account with 2 payments left, and during recent attempts to move my phone line, the confirmation thing that they've sent for my approval of the transfer has repeatedly shown this "wrong" phone that I, again, never actually laid my hands on, as being the phone attached to my current number that they're trying to transfer. I refuse to let my bill needlessly climb for another 2 months until it marks as "fully paid" when it's not even the phone I'm using, and literally every single problem and mistake that has led to and fueled this situation has been entirely the fault of Xfinity.