Horrible service by Avis

Horrible service by Avis, I signed agreement of a total amount including deposit a day before returning the car another deposit was deducted which was such an inconvenient I couldn't even put petrol due to double deposit they deducted. This was Sunday last week, I still haven't received my deposit and I called the AVIS and was told the OR Tambo branch made a mistake and deducted another deposit, a week later I still haven't received my money back. Lady at Avis said they system error she will ask Manager to call me back, I am still waiting.