Please read this thread... I would print out and/or forward the documents posted to them.
http://www.camaro5.com/forums/showthread.php?t=21558
The current recommendation is talk to your dealer. Tell him to check his communications from GM and that your price was supposed to be protected. He can call the DBC to get more info. If he disagrees, call the cusomer service line. Explain your issue and ask them to contact your dealer and explain the price protection to your dealer. If your dealer STILL refuses, you don't have much choice but to either pay the higher price or walk.