deposits on car hire

Hired a car from Euro cars on n Wednesday, Thursday, Friday morning car went back. Went on boat cruise on weekend on Monday when i needed a car again and Euro cars needed an deposit again on new car because they could not use the same deposit for the second car after 3 day. How can they expect the customer must pay there big deposits every time if they did not even repaid the first deposit.They informed me its a new contract they need a new deposit.Is it so difficult to keep give an customer the credit of using the same deposit on an car in cases like that.I think because customers supported Euro cars in the first place they can make exception of giving customers advantage to use the same deposit and make arrangement to keep Your customer happy. My Taxi to a mall and back to guesthouse and then to Airport on the Monday and Tuesday was double the price of the car hire, because Euro cars needed an another deposit for a new contract and couldn't arrange or make exceptions. Its ridicules.