Damaged car rented out

I hired a car on Friday it said on the form it had a few dents. It steered badly on the drive from Airport. I parked it up for 2 days as I really didn't like the way it drove. And drove my Fathers. When I went to drive it 2 days later I noticed the sill bashed and wheels missing chunks as clearly the previous driver broadsided something which left it steering to the left. When I fist returned it the SIXT agent assumed it was my damage and once I handed him the paperwork he apologized and agreed it was not me.. I just received an email from SIXT and they informed me that the car has been rented out the day I returned it and been declared fit for the Road. All I can say is avoid SIxt as they rent out some un-roadworthy cars.