Contract Cancellation but still being billed!

I regret ever opening a contract with Vodacom, I've made an early cancelation of my contract, I was given an amount to settle of R9 600.00 which I've paid and sent back the proof of payment with signed quotation. Only to find out on my credit score I owe them the same amount. Calling Vodacom has been a nightmare, from each department no one knows why that amount even the cancelation department is confused. Such services is terrible, the only thing Vodacom enjoys is taking money and more money. How can I be billed for something that I've paid for and settled. I DON'T KNOW HOW TO ESCALATE THIS ISSUE. I'm totally disappointed and disgusted.