Cell C ripping me off!

Dear Cell C, how much more do I need to pay to settle the account? My contract ended on 31 May, I reversed the 409 which was due that month thinking I was done with the payment. You took my debt to HP attorneys within a month and they informed me I needed to pay R479 and your agents also said the same amount. I paid the amount and still got smses that I still have outstanding amounts. I called my cell c to enquire about those and was told there was nothing outstanding. This morning I got a call from a very rude agent (+***) telling me I need to pay an extra 479 which she can't explain what it was for. I asked what it was for as I made payment and sent proof of payment to HP attornies (*** & ***). So what more do you guys want from me?