Stop pestering me. I've got things to do

I serve. I'm a union steward at a federal agency. And folks love to call me whenever they've got a bug (or a cob) up their a** and think that I live to drop everything just to hear their whine.
I thought I had MADE IT when I started to tell people, if you want to speak with me, send me a message via email and set up time for an appointment. Don't just stop by on your way to the toilet with a "quick question," for me to answer on the spot. Most questions do not have black-and-white answers and most of the time the information given in the question is incomplete or intentionally withheld.
I have to remind myself why I do these things. I have seen good people being bullied and I never liked it. I have also seen people put targets on the backs of others. And that also bites.