Thrifty Car Rental is *******

I rented out a car with Thrifty Car Rental in Durban 146 Florence Nzama Street on the 23/08/19 and returned it on the 27/08/19.On my way home I realized that fuel wasn't full on the car it was below half tank, and I had to fill it up with my money. Upon returning the car I told them about this and gave them my filling station receipt and showed them the picture I took of fuel level. Still Thrifty deducted money from my account as if they have given me the car full. Till today they have not paid my money back, only telling me they are still investigating the matter.