ALSO... SO many places, particularly gov't places, have signage that says that they do not tolerate ANY abuse of staff. Make sure that you say something like that!!! My mom has a roll of toilet paper that says "John Wayne Toilet Paper... It doesn't take CRAP off anyone!!!"
Good luck! I wish you all the best!
Edited to add: And don't you wish that you were mean enough back to just say "Oh, You don't like it? What can I do? Nothing? Then take your money and I'll keep your d***** cake!!!!"