Automatic Transmission problems of the 2011 Buick Lacrosse

Upon leaving dealership after purchase of new car, turned right to exit and transmission jumped into neutral, almost rear-ended. Thought I may have hit shifter. Another turn from stop and trans jumped into neutral during turn while entering traffic. Just missed being hit and perhaps killed. Manually returned to "d". Life threatening defect. Ret to dealer and demonstrated. Next day dealer advised that a "module" on the transmission was installed backwards by gm mfg. Advised gm day after occurrence. Later gm called and told me car had been repaired and get it or "they" would charge me storage. Obviously, after exposing wife and myself to great risk, we did not want that vehicle. Now gm will not speak to me as I try to ensure that the autos produced prior and post to mine were verified to ensure they did not have the same life threatening defect and react accordingly. Gm seems not to care. Pls note: the car "dropped" from drive in neutral everytime I accelerated from a turn into traffic. This problem was demonstrated to the dealer; dealer said park it now. Question is how many Buicks were manufactured with this very dangerous defect. The 2 times this happened, prior to knowledge of the/a problem, if I had not been able to return to "drive" and proceed with maximum acceleration, we would have been unquestionably hit by approaching cars. Had my wife been driving, her reaction would have been slower and she could have easily been killed. This is life threatening. I delayed contacting the ntsb in that I believed gm would take action. I do not believe that to be the situation. Help - lives are definitely at risk if any cars prior to or after mine have this defect. Suspect poorly trained individual on the line that day "filling" in. Poor engineering as dealer stated the part was so designed as it could be installed backwards. Please confirm you are taking action as this is a critical defect that could very easily result in death or serious injury as I cannot confirm gm action.