RCS ripping me off

On the 28th August 2020, I paid RCS loan R600 which is more than the outstanding amount. On the 31st August I forwarded my proof of payment and asked them about the status of my account. Again on the 4th September I asked them how much I owe. I noticed after receiving a statement on the 11th September that I have a credit balance. I requested a refund from my credit balance they told me I need to send a Bank confirmation but they deduct debit order on my account surely they do have my banking details. And I also received an e-mail that they will deducting R70.00 every month on credit balance. I can assume they are delaying my refund they what to earn fee from me. They want me to send them my ID copies as if I am applying for new loan.