Unclear Fees on Transacting with FNB

I have been contacting FNB to reverse fees that have been charged on my cheque account. I was told that these fees are "Honoring fees" for transactions that occurred on my account. I do not have an overdraft facility and am unable to transact if funds are unavailable. So when i queried these fees, i was told that i transacted without funds available and when it cleared they charged the fee as if they ensured the payment was done yet i only transacted when i have funds available. I am now in a back and forth fight with them not understanding that is was not the case. I am hoping that FNB understands the importance of customer service and someone calls me back as I have been trying to speak to someone and the call just rings and then cuts off.