My dealer is ripping me off

I went into my local Caddillac dealer back in July and saw my 2004 with 11,000 miles on it on the floor of the used car showroom. A salesman came up who I did not know and told me about the car and the fact that it was a certified used car. The showroom had many banners as well hanging from the ceiling saying certified used cars. I then went back the next month and the car was still on the floor. The salesman I knew started to tell me about the car and I bought it. During the sit down in his office he mentioned it was a certified used car. I take delivery of it onstar gives me my first 3 months of service free because its certified. Now a month later I'm in for service and the service writter tells me the records still show the former owners name and no mention of extended service. I cornered my salesman in the service area who said they were still processing it. Now two and a half months later I call and he tells me where is it written on the order that it is certified? I said I don't know where its written but up until this point it was believed to of been certified. He says it isn't! I figured if the vehilce met the criteria which this car does, had certified vehicle signs all over hanging from the ceiling and was verbally told it was on more than one occasion, didn't know I have to have additional legal wording. He said "besides you won't have it that long anyways". He is right but it enhances its value with the extended warrenty. How would you handle this situation?