FNB stole R50000 from my mother inlaw

My mother in law transfered an amount of R50000 inside FNB bank in Newcastle but she transferred it to the wrong account.The account she transferred the money to was her son's account which was an account which was under bad debt and no longer in use. This happened in 2020.To this day FNB has not reversed the money. I don't understand what the hold up is.surely if a client reports that she transferred money into an incorrect account the financial institution should be able to assist in getting that money back.tge money is sitting in an account that is no longer being used..