Avis - No return of Deposit

I am extremely annoyed with Avis Car Rental who normally offer a professional service. I rented a vehicle at Cape Town International Airport which was already paid for with my Mango ticket. the consultant went on to charge me again and take a holding deposit of just over R2.3K on my credit card. Once I returned home to Jhb, I queried this with Avis customer care whereby the consultant confirmed that the Mango voucher will be immediately redeemed and my deposit returned in 5days. It has now been 10days and neither situation has been corrected. I called Avis again only to be cut-off twice. Extremely annoyed and disappointed, I expect better from a professional company!