Very very bad service

I rented a car from avis. I took the car back on the the that it had to be back at avis on 30 june. I was told that my petrol deposit will be paid back to me within 6 working days. This is now the 6th day. After making sure with may back the money have not been paid into may bank. I then phone avis call centre and they told me that the deposit details and information have not been given to them yet and i must wait for the finance deparment to get an answer. This is of the worst service i have ever received. You ca not even call it service. I had to pay the deposit money i cash before i could receive the car but they expect me to wait for how long to get my deposit money back.