One of the biggest things with this is that it is an american company. Because they are in mexico, the company should have some type of code of ethics policy for working outside the US. They must adhere to the norms of where the company is at however, they must also go by the organizational norms. If I were you, I would talk to the Human Resource department about the issue and if you get nowwhere with them, you can go to the to the courts or the EEO in the US might be able to help you with the problem.  http://www.eeoc.gov/