Enterprise Rent-A-Car fraudulent charges and refusal to address complaint Nationwide

I just want to add to the reply, that depending upon the benefits of your insurance (such as comprehensive and collision) and a possible credit card used to initiate and complete payment for the rental, it may be wise (and required) to waive the rental company's insurance to relieve yourself of out-of-pocket expenses for damages.

Your primary insurance may cover you for the damages, and your credit card may cover you for the deductible and the "loss of use" which the rental company undergoes while the car is out for repair.

It's better than paying twice for benefits you already may have.

Just be aware of your insurance benefits/requirements to obtain them; and your credit card benefits/requirements to obtain them.

Okay, I saw nothing that stated that you did not cause damage on the vehicle. So the question of damage being there is a fact. Another fact is that you agreed to this damage made to the vehicle while it was on rental to you. So lets get down to what you are complaining about.
You do not own the rental car, enterprise does. And when the vehicle is no longer rented, it is sold. Therefore the car must have all repairs done to manufacture's specification to make it able to be sold after it is used as a rental. It is not your own car where you can just live with a dent or scratch instead of repairing it. Therefore every piece of damage must be repaired.
Enterprise did make a file on your insurance and your insurance agreed to pay for your damages. That is why you only paid out $500 instead of the $900 worth of damage. That $500 is your deductible that you have with your insurance company. Hopefully you know what a deductible is. If you had totaled the rental vehicle you would have only paid $500 (your deductible) and the insurance company would pay the other $20,000. In this case you paid $500 and the insurance company paid $400. If your ins.co. did not agree with the damage assessment on the vehicle (their adjuster inspected the vehicle), then they would have not agreed to pay the other $400. So if you have a grip on the amount to fix the damage, then take that up with your insurance company, or the cost of car parts, or the cost of repair labor.
This could have all been avoided if you had taken the optional damage waiver offered in the rental contract. That waiver would have allowed you make Enterprise eat the cost for the damage you caused ( up to the cost of the entire car ) and not charge you for any time the vehicle was in a shop and not able to be rented. Yes, the $900 charge also included the time the car was in the shop being repaired and not able to be making money for the company while on rent. You refused the damage waiver that would have cost about $14 a day, and therefore made you 100% responsible for the car and any damage made.