Vodacom ******** and POOR servise

Seem's there are a lot of cases such as mine. I had a contract with Vodacom years ago. Upon my cancellation I was almost forced into changing my package to I could pay less. I then refused to do as such as just wanted to cancel the account. Quite a while after the fact I received a call stating that my account was in arrears. I explained to the agent that my contract was cancelled months before and they need to stop this immediately. I then realise upon moving to a new property, they added the areas or seems like penalties for cancelling the account to my credit score. I've tried to speak to multiple agents and was told that it was already sent to the legal department. I phoned the legal department and they then told me that they don't have my account. Again phoned customer service and got the same thing again. We as people work really hard to keep our credit records clean in order for us to move forward in life. I am sorry to say but with signing up with Vodacom that will not be possible. What can be done about this? I need this to be removed from my credit score for me to be able to apply for the next property I want to move to or apply for a home loan. HELP!!!