scammed my son

My son had to rent a car for over a month.  The people who hit his car claimed all liability.  My son should have had a zero balance, however I feel enterprise scammed him by having him sign for insurance of $22.50/day (claiming it was $26/day when called 7/27/16).   All my son remembers is being told to sign and initial- NOT being told they were charging him money for insurance for over a month.  My son drove the vehicle without incident for 24 days, and it sat in my driveway while he was out of town for the other 17 days.  I filed a complaint with corporate, but enterprise should not be allowed to scam people in this way.