Cancellation of Vodacom account

I have bee trying to cancel a contract for almost a year. each and every time I try to phone them, they tell me they will escalade the cancellation, as they can see that I have tried to do so, and reimburse me, and sill nothing. I have stop the debit order, but they just keep on deducting from my account every month! I have been to shops, they just make the same call from my phone, without any success. What more can I do???? A year of paying for something I could have stop a year ago. In this difficult times.