Sent to collections after cancelling

Please help!!! I cancelled services in July. Paid my bill I’m full and turned in equipment. Then I started getting calls on “my account” with an amount due. Spoke to a Comcast rep in October. He verified that my account was indeed marked for cancellation on 7/15, I was paid in full and they showed receipt of my equipment. He said everything would be removed. Now 12/1 I get a letter from a collections agency stating we’ve been sent to collections by Comcast. They said it would take 32 DAYS for a response from Comcast!!!! Meanwhile we’re trying to refinance our home!! Every time I call Comcast now it automatically transfers me to the collections company. Can I PLEASE get a direct number so I can get this cleared up NOW!!!