More than 50% interest charged in one month. They can't tell me why

I'd like to vent my frustration with Game/Dion Wired.

I had a balance of R0.00 on my Dion/Game store card. I don't owe them anything, but I am now being charged an interest rate in excess of 50% that's reflected in my statement. I called to find out how that's possible. They told me that even though my balance is R0.00 I still have to pay a monthly service fee, as well as a consumer insurance fee - and the interest I'm being charged is actually on that. Now, the interest I'm charged is almost equal to the combination of those amounts. This means that I was effectively charged an interest rate of about 100% in one month (100.29% to be exact). In what world is this possible? I asked how they can charge so much in one month - she referred me to section 10 of the Terms and Conditions document, which she said that it states that the interest will accrue daily on accounts that have a balance of 0.00 but haven't been settled. She says that according to their policy, to settle an account, you actually have to call in and ask for a settlement amount even if you don't owe them anything. For context, I owed them R6300 last month and I paid it off. This month I owe them R0.00 but the interest I'm being charged on my zero balance is just R10 shy of the interest amount I was charged when I owed R6300 last month. I found this to be absolutely absurd. At some point during my questions to her, she put me on hold for almost 15 mins which I thought was just ridiculous. The actual amounts I'm talking about are really small, but when you convert it to percentages, that number is high. For me it's a matter of principle and financial providers doing what's right and within the constraints of the law. Anyway, I found her answers to my questions to be outlandish, so I requested to have a copy of the phone call with the intention of reporting them to an ombudsman. She told me that to obtain a copy of the call recording, I need to get lawyers to request it from them. I was shocked by this response. Why do I need to get lawyers to request a copy of a call recording? She said that's their policy, and again, I found this to be ridiculous. I asked for a reference number for the phone call. I then called my attorneys and explained the situation to them, and asked if they could request for a copy of the phone call on my behalf. They asked me what format it's needed, who it should be addressed to, if they need to show a power of attorney letter from me etc. I didn't have the answers to the questions so I decided to phone the call center back so that I could understand what's needed from my lawyers to get a copy of the call recording. The lady I spoke to said that I don't need a lawyer to get a copy of my call recording. She said that I just need to request it, and state the reasons why I am requesting it, and they will send it to me. I was shocked, as it seems I was initially fed misinformation. I assume the first lady I spoke to wanted to deter me from getting a copy of the call recording. I explained to the second lady I was speaking to what my queries were. She too gave me an answer which I feel also didn't hold water. The amount I have spent on airtime and the effort I'm putting in is far greater than what I actually owe. But again, this is a matter of principle. I just want to know why nobody can explain why I'm being charged interest on a zero balance, and why was I given information that let me to make a frivolous call to my lawyers?