Another outstanding amount

To whom it may concern<br> <br> Last year August I cancelled my contract. There were issues with this. I now have received an email stating I still owe money to Vodacom And they are handing me over. I remember clearly paying double my amount last year to have this issue resolved. Vodacom owed me money back from my payments made but now I owe them more.<br> <br> I am extremely unhappy with the service and hope someone can clarify why I need to pay when I cancelled my contract