Thrifty Car Rental Overcharged me Nationwide

I rented a car from Thrifty for 4 days. I needed to extend the rental for a couple more days, so I called to find out how much it would be. I asked the woman for the TOTAL amount I would be charged per day to extend it. She said it was $31.26 per day for each day. I told her I don't want the daily rate, I want the TOTAL charge. She replied $31.26 per day. I asked her is there any other charges and she said no. When I returned to car on the 8th day, they charged me approximately $90 per day. On my first complaint, they refunded the full cost. 2 days later, Thrifty dipped back into my account and withdrew $1008.70. According to what the first woman told me, the total charged should have been $565.00. When I returned the car, they charged me $786.70. But they withdrew $1008.70 from my account. Highly upset, I called customer service back and spoke with Shaun employee# SHAUN4173 and he had an I don't care, you have to pay what we charged you attitude. Also, he refused to allow me to speak with his supervisor Tracy. These people are scam artist. Do not trust them with your account information.