Do I have a case?

I have been working for my current employer for almost eight years and have been in the industry for almost eleven years. I have was fixing a line of copiers, say brand "x", for all the years I've been with this company and I recently got trained on a new line of copiers, let's call it brand "y". I've been trained on only three different models in the brand "y" line, but my bosses are making me work on the models I haven't been trained on and they specifically told me that I wouldn't have to work on the machines I am not trained on. When they do make me go out to fix these machines and I remind them of the fact that I am not trained or certified to work on them they usually give me an attitude and make me feel like I'm going to lose my job if I don't fix the machines. Do I have a case against them if I decide to leave my job?