Refund Not Paid

Rented a car with Avis at Cape international airport, returned the car after four day as per contract in perfect condition. As per agreement and according to staff on enquiry the refund has to be paid back to my credit card in 3 to 7 days. I'm still waiting for my money its now day 10 I called Avis customers care and the agent said they don't know what is causing the delay. They told me Avis already okayed the payment and it could be their bank Nedbank\s fault. They said I must wait 48 hours well I waited still no money back what now??? I need my money back. I'm not sure what kind of scheme this is but when a company is contractual obligated to refund a customer they must do it in the stipulated time. Someone from Avis has to take responsibility and pay me back they can't just blame someone else