get out of something

(verb) to break a commitment, to avoid doing something you had already planned

Example Sentence:

I have plans tonight, but I can get out of them if you need me to help you.

Thomas was supposed to take his mom to an appointment, but he got out of it when he had to work.

A: Are you still going to volunteer today?
B: No, I can’t. I’m too busy.
A: You can’t keep getting out of it all the time. You promised them you would volunteer!

Related:

Similar idioms:

1. better late than never
2. bite off more than one can chew
3. better safe than sorry
4. break one’s back
5. ace a test