Money ****** from my account!

I am fuming! I have been an Edgars account holder since the early 90s and until last month, I had a zero account balance. At the end of April 2021, I inadvertently made a payment to my account, which put my account at R130 in credit. I noticed that on my May statement, that I was charged R30 for a "purchase" that I never made, and that R30 was deducted from the credit balance in my account. This is blatant theft! I called the customer care line, and was told that there was nothing that they could do. The operator told me to complain to the CEO of RCS and gave me his email address. I am gobsmacked that this kind of **************** is allowed to take place. What steps can I take to remedy this?