Price lock plan = Disaster to cancel

I have given notice a month before the 24 months were over, that I want to cancel my plan as well as my subscription to DSTV. 2 x Months later the debit orders were still going off as they never sent my request through to the debit order department, now almost a year later, they have a debt recovery company phoning me about my outstanding account, every time I phone the call centre; they will escalate my query as the account has been suspended, the more I explain that I want it CANCELLED the less they understand. I have reconciled my account (which states that I have paid 24 x months as per fixed period contract) they never did their part in complying with my request to cancel.