Billed even after cancelling service

I have been a member of Xfinity since 2022. In October 2025, I had called customer support to terminate my WiFi connection since I was moving on to a new service provided that had better, and more affordable plans. I was connected to a customer support agent who initially tried to pursue me to not cancel my subscription, but I had made it clear that I was not interested and had made up my mind and would like to cancel my subscription. After being on the line for quite a bit, I was told that my plan was cancelled and that I do not have any balance overdue and since I had my own modem and did not need to return it. I was all set. It's January 2026, almost three months since, and I have been getting calls from Xfinity that I allegedly have outstanding balances that I need to pay, even mentioning that the outstanding account will be sent to debt collection. On top of that, I have been getting calls all day everyday in the last couple days which is extremely annoying. Now, I will not pay a dime for something I do not owe. Either you resolve this or I will be forced to take legal action from my end. Thanks and have a great day!