enterprise rent a car accused me of a dent to right fender /vertical crease about 5-6 inches long bradenton, Florida

on 1/28/2013 i rented a car from enterprise rent a car and at that time i declined to take the extra accident ins. after i left the parking lot i went and did a few errands and returned to my home and did not leave my home again until 1/30/2013 to return to enterprise and wanted to take out the additional accident ins.at that time a rep. went out to check the car and came back in and told me that there was a dent on the right passaenger side fender about 5/6 inc.long. i said that cant be because i never left my driveway until today so if there a dent then it had to be there when i rented it.he said on the day you rented the car did you or did you not decline extra ins. i said yes but i havent driven it anywere its been parked in my driveway until today when i decided to come in and take out the extra ins. he told im sorry but we have to report it to your ins.and you will have to pay for the damages.i belive with all my heart that that dent was there before i even left the lot.the rep. said that you dont even have to be in the car to have damage to the car.i found this sight because i was looking to pay my bill but after reading all the reports that other people have had the same problem as me im going to hold off until i hear from someone in reguards to my problem. everyone that i spoke to about this told me that i was being scamed and that i shouldnt pay enterprise a penny.and im not until i get to talk to someone about it.