Debit order cancellation

Vodacom has been debiting my account with an amount of R124.99 for over a year now. When I speak to their agents they are not picking it up on their system and cannot cancel the debit order. This is highway *******. I wonder how many other customers are losing money at the hands of Vodacom. I don't understand how you can debit someone's account but don't have their details on your system.