Complaint: Debit order on cancelled contract ***

Why is MTN abusing the fact that they have access to my banking details, how do you justify a R320 debit order on a contract I cancelled, when the original contract was R199!!!I cancelled the contract on *** on 25 November. "A cancellation request has been logged, reference number:***.~A.Sc", reverse that debit order and deactivate that contract number I really dont care otherwise I am escalating this to Ombudsman