Avis Damage Loss Insurance Charge not Approved

As a (now past) preferred Avis customer I booked a car on Aeroplan points and was treated as a preferred customer, by not having to sign before picking up the car etc. Shockingly they charged me insurance coverage without asking me - as I have 100% coverage on my Visa card I would not have purchased this option. Never was asked to sign for it. Never initialed anywhere for it. Now I have a bill for almost $500 for a FREE car rental on Aeroplan points. WOW!!! I went to every level of customer service available through Avis and they won't budge. NO ACCIDENT, NO DAMAGE TO THE CAR, NO COST TO AVIS - they issue their own insurance at no direct cost to them and they still will no reimburse me this abount. They will never get anymore of my weekly business again.