Hours texting w support about billing mistake - got my verification number - and now you send me to collections?

Hello! I quit Comcast/Xfinity on JANUARY 27 2025.  My husband took ALL THE EQUIPMENT back to your store and told your employee that WE WERE CLOSING THE ACCOUNT. All was well, all equipment returned. We have the receipt!  We had paid ahead in December for January and expected a partial January refund.   YOU MADE A MISTAKE. You continued to bill our credit card. We communicated with you multiple times, and then with our credit card company, which looked at the evidence and reversed the charges.  You didn't pay any attention, still have an amount due on the closed account, and have now possible sent me to a collections company - Sequium - with a shady non-secure HTTP website that my browser cautions against visiting. If you did this, please call them off them immediately. (If not, they are scammers who could have been tipped off by your many support employees we have texted with?  Shady looking.)  I was on texts for a long time with your support team last week and got a confirmation case number from a rep who agreed that we had paid through January and that we had QUIT JANUARY 27th   (After being escalated twice by other agents, he finally gave me a number!  I also have the chat transcript)   This is so simple.  The charges are a mistake and if you have sent us to collections, that is a mistake too.  Help!