Hyde Park Corner ATM Dispute(Lost Money inside the ATM Machine)

30th March I went to Hyde Park Corner as I wanted to make the deposit into my account to pay transport that will take us to the funeral. So there's only one FNB ATM there, I had R6500 in cash when I left home and I put it inside the machine it only registered R5400 and didn't return the other amount. I thought I was going crazy because where did the other amount went to? I went to make the deposit again in July I left home with R4700 same ATM in Hyde Park Corner I deposited the money it only registered R4500 same thing that happened in March. I then went to FNB Hyde Park Branch to lay a complain. Completed the ATM form dispute. And their feedback was that there's nothing wrong or faulty with the ATM and they can't do anything. When I asked how is it possible because it didn't just happen once, where did the money go? Because I have lost my money to the ATM and it can't be located. Please help how does one get help in this regard.