Dispute on car deposit

On the 20 April 2018 we landed in Durban and rented two cars from Select Cars And Van Rentals. Firstly the sales person miscalculated and charged us double for car deposit as if that wasn't enough they only paid back the first car deposit and haven't paid back my other outstanding deposit. Been calling them without any feedback from them. They are not even bothered to even communicate. I have to call them all the time. Now please tell me if that's not bad service. Its been over a month and I am in constant agony for what is rightfully mine. Where is justice in this though.