cancelled contract still showing i owe cell c money

hi i recently did a credit check and saw that there was an amount showing i owe to cell c for a contract i cancelled long time ago now my credit ratings been down ever since ...called in and they say i must wait till my debit order goes off that is for the other contract i have ..witch doesn't made sense because the debit order of the other contract wasn't the dispute so y wait for the debit to go off when the dispute is about a old cancelled contract