Struggling to get deposito back from Avis

On the 19th of November I rented a small car from Avis/Budget cars in Bellville. (Tygervally) I returned the car in a spotless condition on Friday 23 November. I was told that the return of my deposito will only show in the next 3-5 days. But Avis never returned my deposito. I mailed them and they told me there might be an issue with the release at the bank and they will get back to me within 2 days. After 2 days I still had no answers. I mailed them again and they took another 2 days to get back to me. They told me that there was no release issue and the issue must be with my bank. I contacted Standard Bank and they informed me that Avis deposited my deposito in their own account on the 28th of November. I have mailed them and again and made numerous calls. This is really bad service from Avis. I dont know what else to think---this is *****ing!