Hertz car rental...beware of their terms and conditions

I recently hired a car from Hertz and was informed they needed to put a R1,650 petrol reserve on my debit card which I agreed to. I subsequently returned the car with a full tank of petrol and received an invoice from Hertz stating I owed them nothing however the R1,650 reserve is still on my account. It's now 2 weeks later and according to my bank it is the vendor (Hertz) that need to release the reserved amount and, after contacting Hertz, was informed it could take anything from 7 to 21 days. Clearly I should have read the fine print before agreeing to the reserve amount although it would have been useful if this had been explained to me verbally. Needless to say I won't be using Hertz again