incorrect billing

I have been receiving letters from tv license advising me to pay an amount of R795 early this year , and then march i decided to make an arrangement to pay an amount of R200 every month till R795 amount gets settled , i did make a payment until June 26 , then i expected my account to be on zero and then pay again November for another year subscription R265 which i was to pay on November all of a sudden they send me an email saying i owe an amount of R467.00 and i don't even know where it is coming from not even the consultants can explain what is it for?<br> <br> please help...