RCS unauthorised debit order

I am furious!! I am a victim of a ****!!! In September an amount of R100 000.00 was deposited into my account with a “RCS loan” reference. Few minutes after I received a sms from the bank informing that the amount was deposited, I received a telephone call from a lady claiming to be a private banker and that her client wrongly deposited money into my account. She requested that I complete forms and pay the money back to her client. I told her that I am no longer talking to her and that I am now phoning FNB *****line. The bank can sort this out. I spoke to the *****line at FNB and they pledged the R100 000.00 in my account until the matter is resolved. Yesterday a debit order in the amount of R3 639.00 went off on my account with reference “RCS loan”. I immediately contacted FNB to reverse the unauthorised debit order!! However now this will reflect negatively on my credit record!!! I have NEVER contacted RCS for a loan and have certainly NEVER signed any application or debit order authorisation! I demand that this matter be sorted out immediately in order to prevent this matter to be referred to the NCR!