8 days to refund my deposit

I hired a vehicle under booking reference E ********** 15 from Avis Cabanas resort through my insurance for use over 30 days.. I paid my deposit on collection and I returned the vehicle on time as Avis reminds you continuously. So they quick to take the deposit and hound you about the return date but when it comes to return my deposit I get a response that it will take 8 days to be refunded. What **** is that? It's confirmed the car is returned perfectly no damage yet I must now wait 8 days for my money back?????? If that's the case I must get 8 days to pay the deposit after collecting the car. This is unfair and I demand my refund. I paid cash and now I must wait almost 2 weeks