I work for a well known mailing service. My problem is that I am working and performing "other duties" than what I originally had applied for in the first place. Keypoints here are: I signed a contract that states specific work hours and a specific job I would be takiing. However, the contract also stated that I must be FLEXIBLE and that the company's hours are due to change. My problem is that I'm tired of being "flexible" and performing other duties. My flexibility has turned into mandatory work now. This takes a toll on me since I still have to fullfill two positions. DO I HAVE A CASE HERE?

Without seeing the contract or having a law degree, it is difficult to comment.

However, since you say that it says you must be flexible, your unwillingness to be flexible could be a termination offense.

It would be extremely rare to have an enforceable contract regarding job duties.