Vodacoms bad service

I cancelled my vodacom contracts a few years ago only to find out 2 months ago that there is money outstanding on the contract i ended. I contacted vodacom and settled the outstanding amount even though i was not sure what it was for? The amount is still showing on my credit score which makes me look bad. I tried again to contact Vodacom but end up being sent around about with no person that can help me telephonically.