Firefly Car Rental (Hertz Car Rental) ridiculous Credit Card Hold!

I recently rented a car from Firefly Car Rental (Hertz Car Renatl) at King Shaka International Airport for 1 day (actually 6 hours). It was a Ford Fiesta for which the rental cost was less than R600, Firefly Car Rental proceed to put a lock on my Credit Card of R18,100, yes you read right R18,100 that will only be lifted in 21 working days, yes you read right again 21 working days!!! The agent at the desk which helped me have not for one moment mentioned a thing about this and when asked and phoned about this a couple of days later they have the attitude of "Sorry, but thats the way it is". NO its not the way it is, all your competitors keep a WAY LESS hold and release it within 2-3 days. ALL please be warned about this ridiculous **** and please check BEFORE you rent a vehicle from these ******!