Hands down worst company/customer service

I was refunded $312 for a mistake that xfinity made. 5 days later my account (that I have never missed a payment on) is in past due status. I look to see why, and they have put the price of the refund THEY GAVE ME on my account as past due. When I called to find out why I received zero help. Was told I have to pay the past due amount because they made a mistake and shouldn’t have refunded me for the original mistake they made. When I told them that makes no sense to look at my account I have always been in perfect standing. How did it make any sense to punish me for a mistake they openly admit to making themselves. I was told there was nothing they could do. I asked to speak to someone higher. I was told no that everyone would tell me the same thing. When I said I would just call back to get someone else to hopefully help me. I was told by the “supervisor” he would just have my number directed back to him and I would get no help. So after being a perfect customer for years, never making a late payment in all those years. They are putting my account in past due status for a mistake they admit was their fault and refuse to fix. Forcing me to close my account because I absolutely refuse to pay something that I did not do and allow my account to go to collections. The “supervisor” was rude, lacked any form of being a decent human being , did nothing but read pre-scripted responses. Nastiest, rudest, most unethical company I have ever had the displeasure of working with. I will never ever recommend this horrific company to anyone. If they can flip on a long time customer who has always been in good standing they will flip on anyone.