Telkom keeps on charging for a cancelled insurance policy

I am super irritated with Telkom. I cancelled the insurance for my previous device in October already. On November's statement the insurance was added again. I called to enquire about this. They ensured me that it will be the last deduction as the insurance is paid in arrears. Atleast it is cancelled I thought. Come December, they want to deduct again. Once again they want to tell me that it is the last instalment. Do you guys understand me when I said.... I AM DONE WITH YOUR INSURANCE. CANCEL IT!!!!! Why is it deducted again? It does not make any sense. Must I reverse the debit order or what must be done for you guys to get the message?