Had to pay for parking that should have been free

I parked in the Grand Central parking lot for 10 minutes knowing that the first 15 minutes are free. They then had a problem with the system and held the person in front up by at least 5 minutes. By the time I got to the front I had exceeded the 15 minutes and was requested to pay R6. I advised the cashier that I shouldn't pay as it is their systems fault that I was held up but she then advised that she can't help and called her superior (Mr Lovell) . Her superior then just insisted that I should pay or move out the way. I asked who would I be waiting for and he just said he don't know. I refused to move as I would be waiting for nobody. He then refused to speak to me, ignored me when I tried to sort something out. The cashier then called somebody else whom advised me that he was the supervisor. He said that he would pay for parking but I still ended up giving the money. This happened to me before and Mr Lovell attitude is what upset me most