Can someone please help me cancel my service?

I have been trying for over a week now to terminate my residential internet service.  I have been on several chats with support assistants on multiple days, each time being assured that my connection has in fact been terminated.  When I point out it is not, and provide proof such as my IP address, and traceroutes showing my requests going through Comcast's systems, either I just get abandoned in the chat, or they get snarky, sometimes even saying that if I don't unplug the coax cable from the wall, I will continue to accrue charges.  Obviously this isn't a solution since my new connection will need to come out of that same wall.

Seeing posts like https://forums.xfinity.com/conversations/billing/impossible-to-cancel-my-services/64c9ef08be184078448a6b98

worries me since I don't seem to be having a unique experience.

I can not move to my new ISP until Comcast fully terminates the connection with my modem.

Can someone please help me get this accomplished.  Its been 10 days, and at this point I am hoping they will eventually kill the connection because I haven't paid my bill.

Thank you