Disconnect phone line -> still get charged -> customer services requires the disconnected phone line for verification

I disconnected my phone line on March 3, and am still getting charged. I am not able to reach a customer service agent through the Xfinity website as the AI agent will only spit out a phone number. The phone number does not work for me.

I am actually able to talk to a real person on the XFinity forum Direct Messaging, but they ironically require me to verify my identity through the phone line they disconnected.