Open a claim with GM, let them know how unhappy you are, and let them know how you are being treated by the service managers (personally, if my wife came home in tears, I would have driven there and punched the service manager in the head). Don't threaten them with a demand to buy back the rig, or Lemon laws, just be firm and demand that you as a customer of GM are not happy and that you feel like you are being treated like crap! And, want your really expensive vehicle fixed so it functions normally.