Wrongfully sent to debt collector

I called to cancel Xfinity Internet service (the only service I had) before I moved out of my old place. I would have LIKED to use a web form to do it, but unfortunately I could only call or go into a store. I disconnected my router and modem (my own equipment) right after, just in case.

A month or few months later, I noticed that I was billed again, even though I had cancelled before the next billing cycle began, and I had a zero balance when I cancelled. It didn't make any sense. I could see in my account that I hadn't used any data or anything either.

Xfinity tried calling me and telling me I had an overdue bill, and when I answered and explained to them that I had cancelled months ago, they wouldn't listen. They said there was nothing on my account showing I had cancelled. SO WHAT WAS I SUPPOSED TO DO IF I COULD ONLY SET UP A PHONE CALL TO CANCEL AND THERE'S NO TRANSCRIPT OF THE CALL??? This is why I would have MUCH preferred a web form! So stupid. Probably this way on purpose.

I went to an Xfinity store and explained the issue, they said it was confirmed to be cancelled. I checked my Xfinity account later, and the billing balance was returned to zero.

Now, even MORE months later, I started getting texts from a debt collector! Like what [Edited: "Language"], I thought this was over, and now this debt collector could affect my credit and all that [Edited: "Language"]?

Xfinity, please call of your debt collector. It's not my fault the person I talked to when I cancelled didn't actually cancel, if that's even the case. I'm not going to pay for internet for somewhere I didn't even live at the time.