Poor Poor service

I rented a car from Avis as i usually do a some of money was debited from my account R3453.09 as a holding deposit, i returned the car on the 09/04/2018 my deposit was to be returned within 7 working days on the 18/04/2018 a sum of R3569.46 was taken from my account by Avis i called Avis Head Office and was advised that they will contact their merchant service provider Nedbank to check with them then revert to me that was more than 72days ago i still have no idea when will be getting my refund, i have another booking for the 26/04/2018 Avis will want to debit again from my account i have been calling your call center day in day out trying to get assisted to no avail, i have lost all hope in Avis.