WHY MUST I PAY FOR AN ATM DISPUTE(MONEY THAT I DIDN'T RECIEVE FROM AN ATM))

I am an FNB Gold Cheque holder of more than 15 years, but starting from this year FNB has been such a headache.My account is currently on -R300.I am even failing to understand why FNB is charging me for an amount that was an ATM Dispute,simply because I did not receive the money from the ATM now I have minus on my account.Seems like FNB is coming with different ways to ***** my money just like the UNPAID OF R30 there were funds in my account.FNB must STOP TRYING TO ***** MONEY FROM ME.