it was good you had the flyer on you or there could have been a real yelling match. Just let it go because it surely didnt bother the other person, or they wouldnt have yelled in the first place, and if you "fume" and take it to heart you will surely put it there one way or another - stroke or heart attack.
The only way to face down someone who "thinks" they hold the power, or even do hold the power is never ever raise your voice, if anything speak softer so they have to lean in to hear you, or are forced to ask you to repeat things. The louder they get, the softer you go until, finally, you just stare at them like they're speaking another language and you start to say, "but, I dont understand", over and over. (as in: "but, I just don't understand, the flyer was very specific about the age, why do I owe??") Do not move away cus the line behind you will grow 50 feet long, and her day will be shot, I can promise you.
of course, that's very mean, but anyone who yells at you in public does ask for a retort. If you're "niceness" is actually sincere, it really not meaness at all, its just trying to resolve a problem for the next person. sharet