sing a different tune

sing a different tune or

whistle a different tune also

sing a new tune  {v. phr.},  {informal}

To talk or act in the opposite way; contradict something said before.

Charles said that all smokers should be expelled from the team but he sang a different tune after the coach caught him smoking.

Syn.:

CHANGE ONE'S TUNE,

DANCE TO ANOTHER TUNE.

Compare:

LAUGH OUT OF THE OTHER SIDE OF ONE'S MOUTH.