If you ever need to cancel comcast, time warner or similar entirely and quickly, just tell them you're going to prison. No joke, it works.
> Me to retention person: Hi, I just switched to AT&T Fiber and I'm up and running, so I want to get rid of my Comcast internet.
> Rentention person: Is this the sort of sitation where you would move your Comcast internet to a new location?
> Me: No.
> Rentention person: Ohh, well in that case, I'll go ahead and cancel you're account. Ok done now.
Literally a 4 minute phone call including automated prompts.
If it doesn't, trying to repair that damage could be an exercise in futility. :/
P.S. there probably going to get a lot of people "going to prison" in the future so the scripts will include questions to out the fakers, who want to cancel without trouble.