mfong, same thing happened to me as described by MSPeconomist. I flew on Air France and was rebooked in O class. I called Delta Customer Care 800-455-2720 and they fixed it -- while on the phone. Have your original and any other receipts also so you can give them all the information they may need. You would think your original ticket number should suffice, but depending on the quality of agent, you may need to provide more information and persistence. Good luck.