Billed AGAIN

Last year I complained about being billed for a car that was already sold. This time I made note to follow the correct procedure and even paid a cancelation fee, as well as emailed them the notice to which they confirmed. A month later they billed me again and gave another different amount as cancelation fee. I have struggled three months now and still they keep on billing me on the 1st of every month. I feel like my personal account is not safe and it feels like my money is being ******. FRUSTRATED BEYOND BELIEF!