Still paying after cancellation

Three months ago I phoned Oneplan to cancell and was informed that I had to cancel in writing via e mail and pay a R100 cancelation fee. I have never in my life heard of a cancelation fee from any insurance company. I refused to pay the cancelation fee and cancelled in writing. Then my problem started. The end of the first month, i had a debit on my account which I reversed. End of the second month I had a double debit after being informed that my account was suspended. Again I had the debit order reversed. Low and behold, at the end of August there was a tripple debit which again I had reversed. I have now put a stop payment on my account to Oneplan but have no guarantee that they will not debit. What amazes me is how they do business without any phones. I say that because NOBODY from Oneplan has bothered phoning me to find out what the problem is, so clearly they don't have any phones. Now I have decided that enough is enough and should they debit my account again at the end of September, I will take the nescesary steps required. Hopefully now someone from Oneplan will phone me and find out what the problem is.