Terrible customer service

I rented a car for the period 09.10.2021 - 11.10.2021. I was informed my holding deposit would be R6000 and I should bring an embrossed card upon collection of the vehicle. When I arrived and was checking out the vehicle I was advised that my holding deposit is now R9500 because I am using a debit card and not a credit card (my debit card is also embrossed) Doesn't make sense to me why I had to pay the increased holding deposit, nonetheless I did as I needed a car to get around and couldn't arrange another vehicle at the time. I returned the vehicle in same condition with a full tank of petrol. I have since called *** about 8 times since yesterday without any success of getting my deposit released. Safe to say this is the last time I will be using thrifty I have never been so inconvenienced with car hire before in my life. If anyone at thrifty values their clients I would appreciate a call to get this resolved.