Credit card rip-off

I contacted FNB related to interest accrued the last 3 months of almost R1000 even though I make full payments before the due date of the 2nd of each month. I've been informed that the interest accrued on my credit card makes no sense and that it will be forwarded to the ***** division for processing. I was also informed that they will provide feedback within 72 hours. It’s a week later and still no response. I phoned today just to be informed that the interest is due to transfers etc. made. What you are basically telling me is that to increase my credit score I have to pay for a card close to R500 rand (R300 for interest and R200 for normal fees) even when I clear the card every month. If this is the case I will close the credit card and will also move to Capitec. I don’t want to bank with bank that really just rips people off.