Double Charged!! No one answers to phones to get reimbursed

I made a prebooking for my vehicle for 4 day in which I paid for prior to leaving my vehicle at the airport. When I returned and was leaving the boom gates would not open in which time the operator said that I should pay R900 AN ADDITIONAL TO WHAT I HAD ALREADY PAID FOR which will be refunded!!! I'm trying to call Airports Company SA the entire morning with NO ONE THERE being able to assist me!!! I don't have the whole day to try and contact you guys to get this sorted out