Enterprise Rental Enterprise Car Rentals Tricked into signing for insurance despite telling them that I dont need it and have AllState coverage COLONIA, New Jersey

I booked a rental car for my wife on 3/21/2011 via enterprise since we were relocating to the west coast and had sold our car and I was already in Oregon at that time.  The booking was from 3/22/2011 to 3/30/2011 since my wife was supposed to fly out of NJ on 3/31. The confirmation number for this booking was SD3VR9.

When my wife went to pick the car she was offered an upgrade which she refused. She was also offered the insurance to which she said that she will be using our existing AllState insurance and showed the Enterprise agent the insurance card also.  The agent duly noted All State in the document and asked my wife to sign and my wife signed it.

The shock for us was when she called me on the evening on 3/30/3011 from the Enterprise office saying that they now want $200 for the insurance since the agent had gotten my wife's signature on the section requesting insurance.  I spoke to the person incharge over the phone from Oregon and he offered to take 3 days off insurance but said that we will be charged insurance for the remaining days.  I could not do anything at that time from Oregon since they had my credit card information anyway.

Someone please let me know how I can stop Enterprise from scamming in this blatant way.  I feel it is shameful and disgraceful for Enterprise to engage in this kind of activity and indulge in such blatant fraud.

Any advice would be much appreciated since I would want Enterprise to reimburse me the insurance cost since my wife told them she had it and did not need it.