Advantage Rent A Car

I rented a Hyundai Sonata on January 30th at about 11 AM in the morning. I waved all insurace coverage and drive off onto Toute 528 Towards Orlando. afew minutes later I had a flat tire. I had to change the tire on this very busy highway and return the vehicle about an hour later. The car was checked in and the flat tire was noted. I was given a free upgrade (Convertable PT Cruiser) for my troubles and returned this car with no further incident on February 3rd, four days later. That was the last I heard or thought about this.
On March 3rd one month later I received a call from Subrogation Management Team located in San Antonio TX. They informed me that they were pursuing a claim for $280 dollars against me on behalf of the Orlando Advantage car rental. The claim was for a broken driver's side mirror on the Hyundai Sonata. That same day I received paper work indicating the damage. The actual damage form was the form I had acknowledged regarding the flat tire. Someone had crossed out flat tire and wrote in "Busted Mirror". I disticntly remmber looking in that mirror as I drove the vehicle back to the car rental. It was not "busted" or broken.
I beleive this is a false claim and i am wondering does anyone know what my rights are? The Subrogation Management Team is some company that is like a "strong Arm" collection agency so the car rental place does not have to waste its own time pursuing claims. I looked over some of the other paperwork, they had a invoice from a body shop that was date February 14th, two weeks after the alleged damage, (January 30th). I find it hard to beleive they ahd that car off the road for two weeks for a broken mirror. I am thinking they are coming after me becasue either an employee broke the mirror or maybe a less collectable renter did and I am taking the fall. I would appreciate any advice anyone can give me.
And do not rent from these guys, nasty people, nasty place.
Thanks.