I'm afraid that you may not have too many rights in this case.  Most employment arrangements are what is known as "at will".  This means that you can work for an employer or not, your choice. In turn, an employer can hire or fire you for any reason or no reason at all, as well has increase/decrease salary/hours, promote/demote, and generally impose requirements as it sees fit.  So whether or not it knew of your responder duties, terminating you for them is not a violation of the law.  Your only hope is if there is a union or employment contract that would prohibit your employer from taking such action, or your termination runs contrary to company policy or constitutes a form of workplace discrimination (which doesn't appear to be the case).