I did tell them, the person I told said I could keep my automatic payments going, which I did for a year before they said I hadn't paid a year on the new addres

I did tell them, the person I told said I could keep my automatic payments going, which I did for a year before they said I hadn't paid a year on the new address and had overpaid a year on the old address. They then denied knowing that I had moved address, but didn't have an answer to "then why have you sent me a letter (to my new address) saying the payments for the old address should be refunded if you think I still live there?" (they literally denied knowing I had moved after sending the letters). I appreciate that involved human incompetence not just a poor IT system, but a better system would have made the updating of me as a person paying council tax from one address to another seamless, then it would have flagged the problem sooner than a year in, and then it could have crossed my "debt" with my "overpayment" rather than passing it (in what I assume was another human mistake, but again allowed by the system) to a debt collection agency.