An inventor is someone who makes a conceptual contribution to something claimed. Provisional applications are not required to have claims so at the time of filing the concept of who is and is not an inventor may not be accurately known.
The charitable explanation is that whatever your contributions was it was deemed not a conceptual contribution to something they ended up claiming. On the other hand many organizations put people on as inventors by a pecking order related to management and profile in the organization.
If you are an inventor of at least one claim, they risk having a defect in the resulting patent due to incorrect inventorship. Until the AIA law that could be a fatal flaw if it no one could swear that it was not by "deceptive intent". Now it is easy to fix without anyone swearing to anything.
To answer your question, if you no longer work for the company you might send an email or letter to the company's outside patent attorney. If you still work for the company I would bring it up with my manager. The angle that it hurts them (not much anymore) to have erroneous inventorship might get you somewhere.
Of course, this is all for glory in that you have presumably signed your rights to this invention and others to the company already.