Slow lounge billing

I took my mom into the Slow lounge in CT about a hour before our flight and was charged R500 for it. I had been in the lounge previously and was not charged at all, hence why I took my mom. I contacted FNB to query the charges and was told I do not qualify for the benefit. When I told her I was there previously she just continued to tell me why I do not qualify. I then received an e-mail to tell me that their systems were down over the first period where I was not charged but that normal charges commenced over that period. I, as a customer, took it that I would not be charged. I am not responsible for their systems running efficiently. For R500, FNB could have kept a customer happy. I wanted to move over my business banking to FNB but will not now. I will most likely move all accounts to another bank and will most certainly not be recommending them to anyone.