Account Incorrectly debited

Last month I had to reverse a debit order for R813 because I have never had an account with MTN for any products. When I tried to follow this up, I am told that I need write a letter or affidavit and some 3 signatures. I don't understand why I have to jump through hoops for something I didn't even initiate. If it was that easy to debit my account then it should be just as easy to call me and get my name out of all this.