Here is what I found in less than a minute by using the Google search engine:
Gerd Klauss, President and CEO Frank Witter, Chief Financial Officer Steve Keyes, Director, Corporate Communications
Address: 3800 Hamlin Road Auburn Hills, MI 48326
Telephone: 248-340-5000 FAX: 248-754-4930
Don't bother with lower level officials. Go to the top.
Send a typed snail-mail letter to one of the above company officers (preferrably the CEO) and do not use email, which tend to be ignored. In the letter, provide as many details as possible, and back it up with documentation. Do not be insulting or threatening, that will just destroy your credibility.
In the end, if you cannot get satisfaction you may have to hire an attorney, and their fees on contingency cases are normally 33 percent or more of the award.