BACK UP

Supply evidence to prove that something is true or reasonable.

That's an interesting theory, but can you back it up with some facts?

BRING UP

Mention or introduce a new topic in a discussion.

The conversation was very pleasant until she brought up politics.

CALL OFF

Cancel.

The baseball game was called off because of the rain.

CUT BACK ON

To reduce.

I've decided to cut back on eating in restaurants to only once a week in order to save some money.