I was upgraded on today's FLL-ORD flight and once the upgrade cleared I have removed my Platinum number and replaced it with Prem Ex. About three hours before the flight I noticed that my upgrade was removed and I was rebooked to Y class. When I called the Platinum line I was told that my PNR was red flagged and revenue management has removed my upgrade. I demanded to be put back in R class and told them to put my OnePass number back in. Has anyone experianced the same situation?