Begging people to either ask what's in a food or just shut up and deal with your mistake in ordering something you were unfamiliar with instead of harassing some person working at the restaurant.
Even if it's their mistake, deal with things calmly. Most people aren't going out of their way to kill you, and you're far more likely to get what you want if you're kind and considerate.
But I keep noticing people just asking for something, not asking for information about it, and then getting mad because it's “not what they want.” It's what you fucking asked for, though.
So... deal with it?
And 'deal with' also means you should “talk kindly to the wait staff once you realise that there's a mistake,” especially if there's an allergy-related problem. It does not mean “expect that this person is a mind-reader and shout them down for giving you exactly what you asked for.”