Avis dont release deposit.

For just over 3 weeks I am trying to get my deposit released from Avis. I have made several phone calls with promises and nothing happened. Sent emails with no response from them. It also seems that they deducted several things afterwards. I did return the car full with petrol. They are *************. I will not make use of them again and would not recommend them. I do t know what to do more to get my money back.