Unfair consumer practices

Hi I took out a credit card with RCS at Makro 2023 and the credit was 10k I bought a fridge with it at Makro and I have been paying varying amounts of money ever since at 1st I was paying 500 until I used the card again to buy groceries with it and started paying 1000 every month till to date but what surprises me Is the were some 2 months in succession where their debit order were not going through and I had to pay manually and when I called them to check why is it they can't seem to know didn't the debit order didn't go through now on their system 3 or 4 months after those manually paid debit orders they picking up that there's a skipped debit order while all my monthly debit orders were all paid they now calling me harassing me threatening to hend me over if I don't pay double my debit order to cover for that skipped debit but I clearly have records showing I didn't skip I actually paid for that month in question they don't even want to listen to me or give me an opportunity to send them prof of all my payments please help me how to go about this problem