Deposit refunds

In the past two months I hired two cars from Thrifty and each time I battle to get my deposit refunded. I booked apnother car with them for the end of January but will be cancelling the car, will see how it goes with the refund. When you fill the vehicle before return they manage to add some more fuel in an already full car and deduct it from your deposit. Their cars are also not in a good condition. I'll rather stick to other rental companies. Nothing good to say about the quality of their vehicles or service. I think it is a dishonest practice...