Enterprise Rent a Car charged for damages not caused by me Independance Missouri

On the second week of October, after my Rv broke down, we rented a car from Enterprise Rent a car in Independance Missouri. I did a walk around in the car a did not see any damage. We continued on our trip to Denver. On ou17:18:50r way back, we dropped off the car and the agent opened the door stood on the threshold with  her head at an angle,  and spotted two dings. She then went to the front of the car, put her head even with the hood and spotted one more ding. She blamed it on Hail damage and since I was responsible I would have to pay for the damage. It did not rain the whole time we were in Denver. On our return we encountered light rain, no hail.  Unfortunately, I can't prove prior damage. Be warned, Enterprise will stick it to you if you do not go over your rental with a fine tooth comb when you pick it up. I have been a customer of them for years.  I will NEVER rent from them again.