Poor service and injustice.!!!!

I took out a contract with them 6 years ago, I sold the car 3 years and call them to cancel, now they have black listed me. When I called them to follow up they said I owed them R2500 cancelation fee with MBD which I had no knowledge of. I tried applying for a home loan and was told that I've I have an account in arreas. I went and checked my balance on clear score it says 1300, now all of a sudden its 2500. Poor service and dishonestly from this company I would NOT URGE ANYONE TO SIGN WITH THEM, BEWARE!!!!