Large companies like to push you around, but like most bullies, they typically fold at the first sign of a fight. You should always ask for what is yours. Don’t shy away from threatening a lawsuit if you need to, but always be nice to the customer service reps, they have no control over the rules, but are more likely to help someone who is friendly.
Today’s New York Times has a cure story about Ralph Nader and his fight with US Airways. Ralph should have stuck to consumer protection.