Debit order going off after account is settled

I called the RCS customer services line on 26/04/2019 for a settlement amount on my account. Immediately after the call, I did an EFT for the amount specified. On 02/05/2019 my bank account was debited by RCS, even though I owed them nothing. I called the customer services line on 06/05/2019 to find out why money was taken from my bank account and the lady I spoke to couldn't really answer my questions. All she told me was what I already know (the amount I paid to settle and the amount that was debited from my account. She advised me to go to my bank to do a reversal or I can use my card to spend the amount that is due to me. Firstly, I do not want to use the card to purchase anything. This is why I settled the account. Secondly, I am not willing to pay fees applicable to the reversal as this is not my fault. I also noted that the amount reflected as owed to me is about 10% of what was debited from my bank account. I would like to have this rectified without having to waste my time by going to the bank to sort out someone else's mess.