Thrifty Car rental holding my money

We have booked car rental for 3 days and paid in full online. Upon arrival at OR Tambo on the day, we were told by Thrifty agent that due to our low credit score he would not be able to rent us any vehicle. He advised us that the money will be credited back to us the very next day. It had been 9 days, 6 emails and a phone call and we haven't received our money back.