Charging for hidden unused services

I canceled my internet services and am being charged for an unused free phone line that was added to my account. I canceled the internet services last year after I noticed I was being overcharged for data. I returned the modem and was told by customer service on the phone that it would be cancelled. They never cancelled the services and I was charged. I called again and it was finally cancelled. This was around September last year. Then, early this year in February I noticed that Xfinity was withdrawing a series of random payments from my account. I called customer service and after an hour they saw that I was being charged for an unused phone line and stated they closed the account. Today, almost four months later, I receive a bill for overdue charges. Can you please get someone to actually help me resolve this issue? This is criminal behavior charging for hidden unused devices after cancellation. Why is it so difficult to get actual customer service to cancel services? Isn’t this considered criminal activity for a business? Please confirm that the overdue charges will be revoked and the account is closed.