Vodacom's cancellation service is useless.

Vodacom's cancellation service is useless.

I’ve been trying for months to cancel a data contract I have with Vodacom. Every month I will phone the cancellations department to find a Vodacom employee who guarantee me that the contract is now cancelled but month after month the debit order is deducting money from my account. Their inability to cancel the contract is costing me money monthly. Can someone competent at Vodacom please assist me.