about face, to do an

do an about-face

To suddenly and completely turn or change one's direction. This phrase can describe one's physical movement or a change in concept. She did an about-face and walked back up the steps once she saw that the subway wasn't running. Based on the reactions we got from test audiences, we need to do an about-face with the movie's plot.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

about face, to do an

To reverse a decision or change one’s opinion. The term comes from the American military command to turn 180 degrees at attention, dating from the mid-nineteenth century, and by 1900 was being used figuratively. A more recent colloquial usage is to do a 180, but it has not yet reached cliché status.
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The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
See also: