Accident Involving their car

We were struck from behind by a car rented from Enterprise on July 8,2012. It took 39 days for  Enterprise who are self insuring to make and offer to settle on our totaled truck. Finally they made an offer that was not only less than half the market value, but far less than the balance owed on the loan used to purchase the vehicle. The upped the offer ,but not enough to pay it off .The claim had to be submitted to our own insurance company ,we had to pay our deductible and they settled the claim  in 2 business days. Enterprise does this apparently trying to cheat victims of their renters with little concern for anything but the buck.