This company is robbing people

I rent a car at Thrifty in Durban on 3 Nov 2017 for 2 days I took a Nissan 7 seater as I was going with my family to a funeral in Ladysmith, I brought it back on a Monday 6Nov 2017 with full tank with no dents. Now when they suppose to deposit back my money they tell stories that I excided km by 900. Fuel was not full. The return trip from Durban to Ladysmith won't come close to ****m. This company is robbing people. They don't want to bring my money back now.