I took my car to a Ford dealership because of an electrical problem. They then diagnosed a bad alternator and installed a new one. When I picked up my car 3 days later, all the paper work I was asked to sign indicated "no charge" beside each of the items repaired or replaced. Two weeks later the dealer called and said I owed $534 for replacement of the alternator. They claim that they forgot to have me sign the paperwork detailing all of the charges when I picked up the car. Can they collect?