Erroneous Charges on my account - Sent to Collections?!

To provide some history - 

I chatted with an associate to add a phone line to my account, late 2025, after unsuccessfully trying to add it myself. They confirmed 3 times that the phone number was going to be the same, at the end of the chat - I checked. It was a completely new phone number. I was being charged for both the incomplete set up and also the new line plus my original line. 

I was told these lines would be canceled but they continued to charge me for BOTH of them. I complained again and was finally able to get them removed and supposedly the bills written off. I switched to AT&T because of the continual issues I have ran into with both Xfinity Mobile and Xfinity Internet. I called in December 2025/January 2026 to cancel my plan. It was confirmed over the phone that it was canceled but continued to receive bills for it. I reached out to complain again, and they assured that those erroneous bills would be written off of my account. 

I confirmed my account was closed and there were no outstanding bills. Recently, I received a $66 bill from a collections agency stating it's for Xfinity Mobile and it showed up on my credit report. I was assured multiple times that this account was closed and the bills were written off. This is absolutely unacceptable and I need you to pull this from collections and the $66 bill written off/canceled.