Deposit refund

The experience of renting a car from first car rental is good but they never return the deposit back on time as per contract. Every time I rent car to get my deposit back I need to remind them which is unfair at my end. This is also unfair because the deposit is charged on the credit car and the bank will calculate the instalment on how I owe when I do not owe that much. I don’t know what sort of **** they are running but please return my deposit first car rental.