They didn't cancel my contract when due

I'm so disappointed, my vodacom contract was coming to an end in May 2020 so I had paid up my balance to cancel my contract on the 9/5/20 once I knew I had paid my contract fully I called in to cancelation department and I was told that it would be canceled,two months later I received a email saying I'm in debt with vodacom and I owe them money cause "I didn't cancel my contract" I have evidence to show that I had followed ever precise steps to cancel my contract but it wasn't canceled I am now in pre legal and every month vodacom still bills me for a contract that was supposed to be canceled when I phoned to cancel it. I have phoned and emailed so many times yet they do not do anything about the situation or try help the customer to get down to the problem I am furious with vodacom because I'm now facing pre-legal and my credit will get blacklisted all because someone in their cancelation department did not do the right procedure to cancel my contract. I will never get anything from or to do with vodacom again!!!!!!!!!