Refusal to cancel insurance

I have sold my car and I am working overseas without a SA number. I have sent 4 emails to cancel my insurance and Miway has continued charging me and instead of contacting me on email they send me an automatic email saying they have tried to contact me without success. This must be one of dumbest things I've seen, when considering I have told them in every email I don't have a SA number. Telephone on this review is my niece's as it is a requirement to have a number.