VODACOM BREACH BUT WANT TO BLACKLIST ME

I had a contract with Vodacom for data. initially it cost me R69 per a month. when the contract was about to expire a call centre agent called me and asked if I wanted to renew it. I told him only if it was going to be capped and only if it was going to be more or less the same price. he offered me a fantastic deal! with even more data at a fixed amount per month. When the first bill came it was over 400!!! I called to complain- no one could help. second month came- same thing! I called again but was shunted around! I eventually cancelled it due to their breach and the sim card has been deactivated. I then wrote to their general customer care line and I was contacted by a manager who said he was going to investigate it and get back to me- this was last year! I still haven't had feedback... next thing I know they are sending me letters of demand every month. and the amount demanded increases with every letter! They don't even have the right physical address on the letter. I have tried to call them but no one will help me. I am disgusted by their unprofessional conduct.