Sunrise credit report - incorrect report - Xfinity claim escalation

I had an accout in my name for Xfinity service at my elderly father's house for many years. When he became terminally ill, I called to stop the services as he was in the hospital and would eventually be discharged to my home for hospice care. He passed away January of this year.

I spoke to Xfinity through the chat to stop the services and a very kind representative said she would clear the last payment due as she could tell he had not used the service (which was internet only) whle he was in the hospital and on hospice.  We closed the account and she said she would clear the balance to $0. I returned the equipment.

I then received a bill reminder and went through the chat again. This time I was upset as I didnt want it incorrectly reported to the credit agency. The rep assured me she would escalate it and the balance would be cleared, nothing was due and nothing was reported late.

I even visited my local store and spoke to someone who added notes to the escalated complaint.

All of this is surely stored in my history with you so can be verified. I also have copied of the chat logs.

Now today I have received a report from my credit report agency saying I had a derogatory mark on my credit report  from Sunrise Credit Services saying in September they added this as a debt sent to collection agency.

This has made my credit score go from excellent to fair.

I have worked very hard to get and maintain an excellent credit score and this is causing me untold stress on top of my grief.

Who can I talk to that will help me to 1) clear this balance and 2) make sure Sunrise retracts their report so my score is reinstated?