Fnb not willing to assist

On the 5th of June 2015 I made a huge payment to momentum from my Fnb account, due to some unforeseen circumstances, I called momentum to get the refund, but I've been getting run around from them and was referred to my bank which is Fnb to do a recall, I called Fnb and they sent me recall forms, I completed them and return back to them, only to be told that they can't revervesed the money because momentum is a public recipient, so now both momentum and my bank cannot assist with the reversal of my own money, as a client of Fnb, I believe they should protect me their client, but it seems like no one is willing to assist. Can you please try to resolve this matter urgently ?