RCS do not want to help me to get my money back after the bank made a mistake

On the 26 of October 2019 I made a loan at FNB to do some revamp on my house so to get the loan the bank must settle all my accounts and one of them is RCS Mass build (builderwarehouse credit card) but the bank made n mistake by to paying dubbel and one of the pay was in a wrong account. In a ref *** the amount R14 200 and not in my account ***. So when i phoned the bank they said i nees to get in touch with Mass build RCS to pay my money back in my account because the bank can't do it. So I Phoned RCS Mass build and they said it is not there problem the money is not reflecting in my account and the bank must do the reversal not RCS. Not one of the company's are willing to help me but i feel it is both FNB and RCS problem to sort this out. And i do not getting any results back from RCS.