Incompetence extravaganza

I had activated a month to month data bundle for the month of June. I contacted Vodacoms call centre to cancel it in July and was advised by the lady that it was cancelled. In August I was again billed for it, I then contacted the call centre again and was AGAIN advised that it has been cancelled. September and I have contacted Vodacom 4 times requesting cancelation. And they have advised it has been cancelled but im about 200% sure that I will again be billed. I would hate to call the staff useless but the incompetence is almost debilitating.