From the jurisdiction where you booked the car from (i.e. your home town). Then get their legal team on the phone and request all the documentation (i.e. the proof of the damage, pictures, plus the turn-in page from when you rented it, etc.). There's probably some stupid mandatory arbitration agreement as part of the rental agreement, but by filing in small claims you might get them to dismiss it (it will cost them more than $1000 to pay a lawyer to deal with you than to defend it) and, at a minimum you could get some actual information from them that you won't get from the collections people.