Vodacom
Billed me for cancelled contract

I requested a premature cancellation on my contract and paid the amount owed on 15 Feb 2013, that means I paid everything I owed for that contract.
End of Feb, my bank account wasn't debited and upon querying I was told there was a payment and my account is in credit.
After explaining and faxing the signed quotation and proof of payment 'again' the contract was eventually terminated on 11 March 2013.
Now I have spoken to just about everyone to find out why I was debited too much end of March and it seems I have been charged for the contract that was cancelled.

I would really like this sorted out