If you don't answer the call after cancelling they don't process your cancellation

Very disappointed and do not recommend Shaw Academy (South Africa). I tried out their free trial, did about 2 lessons before I decided that I didn't want to continue. Cancelled my trial subscription on their platform, they kept trying to call to discuss, I then sent an email response saying I confirm my cancellation and do not wish to discuss telepathically. A few weeks later I my bank account gets debited with a subscription fee and upon logging in it is clear that my cancellation was never authorized. I have had back and forth mails with them where they refuse to acknowledge my 1st cancellation and say they are following their Ts&Cs so will not refund the amount. They have now not responded to me and am not sure how to take this matter further. ARGHHHH!