Alamo Rent A Car National, Vanguard letter saying I hit their rental when I wasn't even in the state! Internet

I received a letter from Alamo Rent-A-Car stating I was responsible for damage to their car driven by their renter in San Diego 11/13/09. I was working an 11-hour shift that day in Oregon, and the last time I was in San Diego was 1970. I believe Alamo is trying to commit fraud on me because I found MANY similiar complaints on the web. I'm in a better position than the stories I've read, because I have proof I wasn't even in the state! I've filed a complaint with the Better Business Bureau, and I urge everyone to do the same. Also the USPS for mail fraud and the FBI. They have to be stopped now! When I told Alamo what I think, they said it would be taken care of, (they would drop it because they knew they'd harassed the WRONG person), but I said I was not going to let this go, THEY are in trouble, and she hung up on me. This was after I asked for the address of the alleged accident so I could get a police report, and she didn't know it.