Unreturned deposit for car rented from Avis

I rented 3 cars from Avis in Cape Town during the festive season. I rented from the 22nd of December until the 6th of January 2019. It is more than 10 days later and my deposit has not yet been returned to me. I enquired twice in the last two weeks and was told an instruction was sent to the bank and if I wanted to escalate the matter I would need to contact my bank and request them to action. Furthermore I was also told that my deposit less my rental would be returned back to my credit card yet I have been charged my full rental and my deposit not yet returned either.