just venting for a moment

Kait
It bothers me when someone tells you one thing and gets you to agree to it, and then changes that thing and expects you to go along with it like it's no big deal, without even asking. 
Like when you agree to babysit one kid and then you find out later it's actually 3.
Or when a few family members are getting together to spend time, for dinner, and then after you've already budgeted for the month, all of a sudden they decide to do something really expensive instead, and tell you it's no big deal because dinner costs that much anyway (which it doesn't) and it potentially kicks you out of the plans. 
Of when you agree to help with something and you ask how the wardrobe is, and they tell you whatever, just wear something nice...and then just a few days before the event they tell you a specific wardrobe that you don't own and can't budget for at this period in time (for something you aren't doing to get paid, just helping out, so can't buy a clothing item out of what they're paying you).
It just really bothers me because it feels so disrespectful and inconsiderate of the other person. 
Just wanted to vent for a second. This seems to have been a trend recently in my life and I'm struggling with how to respond to this in a kind way, because it just makes me want to give a snarky, rude answer that makes them feel bad, and that's not a good thing. Learning how to deal with this one is a hard lesson.