change one's tune
To make a change in your story, statement, or claim; change your way of acting.
Изменить отношение к чему-либо; поменять мнение или образ действий.
The man said he was innocent, but when they found the stolen money in his pocket he changed his tune.
Bob was rude to his teacher, but she threatened to tell the principal and he changed his tune.
You are going to fail if you don’t change your tune.
Ты потерпишь неудачу, если не изменишь своего отношения к ситуации (или поведение).
change up
To alter or switch something, especially from a usual method or proceedings. In this usage, change it up is commonly used.
I've had this haircut for awhile now, so I think it's time to change it up.
You should change up your material so people don't get bored with it.
To change to a higher gear while driving.
You'll probably need to change up once you get on the highway.
To pitch a ball at less than full speed in baseball. Usually used with on.
John pitched a ball that was very fast and the batter missed it. Then he changed up on the next pitch and the batter was badly fooled.
going through changes
To be in trouble, to have difficulties, to be trapped in unfavorable circumstances.
"What's the matter with Joe?" - "He's going through changes."
ring the changes
To say or do the same thing in different ways; repeat the same idea in many ways.
David wanted a new bicycle and he kept ringing the changes on it all day until his parents got angry at him.
A smart girl saves money on clothes by learning to ring the changes on a few dresses and clothes.
shortchange
To return less money to a customer in a store than is coming to him or her; cheat.
I was shortchanged by the cashier when I got seven dollars back instead of eight.