I had a similar problem once except that the agent had somehow booked me in two seats on the same itinerary. (seated next to myself even) There was nothing the agent could do at the airport but a letter to customer service with a followup call was an easy remedy. They appologised for the mistake and credited my CC.

And as much as AS screwed up in your instance, i will remind everyone that calling at least 24hrs ahead to confirm your reservation IS a responsibility of the traveller. (although I am guilty of not calling most of the time too). Hopefully AS will make good on its customer service promise.

-rollyo11