After Xfinity accepted liability, my account was marked for collection

I had signed up for autopay on my credit card. I did not receive the service I signed up for in april.  I disconnected service in May. I called customer service, I was told I would be refunded. I noticed that I was charged on my credit card in May even after disconnection and no refund. I called customer service again and was given the run around.  Twice the agent's just hung up on me.  I have called about 5 times and spent 12 + hours on the phone. Ultimately,I disputed the charge on my card and attached proof. Credit card told me that Xfinity accepted liability and credit card issued a dispute resolution letter in my favor. I learnt today that my account was marked for collection. My credit score tanked. I called Xfinity today. I was told to go in person to a Xfinity store and perhaps the manager there would help me. Agent said he would try to mark my account as normal.  One agent said I spoke to 3rd party agent a customer service and xfinity would not honor anything they said. The real agents supposedly overrule the 3rd party customer service agents. Moreover, no supervisor's are available, left early , sick, not responding. 12+ hours, hoping customer's will just tire. No email to mail proof and hours waiting for agent to come on the line.Once the DM open's up I would like to submit the credit card's dispute resolution letter.