Continued billing after cancellation

Hello,

I canceled services in July 2024. I continued to be billed until October 2024. At the time of cancellation I was told I had no balance due. I also had auto-pay enable, and Comcast disabled my auto-pay on their end when I canceled. However, I continued being billed. I have called multiple times and have been assured by customer service that the charges will be removed and the collection agency that has been contacting me will be notified of the mistake. The agent who assisted me today told me he was unable to access certain parts of my account and that I needed to call a different number. He provided me the number [Edit: "Personal Information"] This number, as far as I can tell, is a fax line. I am not sure why I was provided this number. A previous agent earlier this year told me he would have the balance removed and the collection agency notified, but I have continued to receive collections notices and when I called Comcast today there was still a balance on my account. 

I would like to be connected with billing resolution in writing so that I do not have to repeatedly call, which is a waste of both my and Comcast's time. Please let me know how I can do this.

Thank you