Exploitation from Europcar

Im insured with Auto n General and unfortunately when I need a car for a certain time I'm referred to Europcar. It's now the 3rd time I've had to pay deposits over and above that I still somehow get billed on my personal account despite returning the vehicle on time and without any defects and with full tank but still I never get refunded the deposits at all times. Do we really have to put up with this exploitation from car rentals and insurance companies coz really quick to take money out however, find it difficult to refund us or render services. This is exploitation needs to come to an end we work hard for money it never grows on trees.