change one's tune

/CH EY1 N JH W AH0 N EH0 S T UW0 N/
verb
  1. 1

    To reconsider; rethink; to reach a different conclusion.

    โ€œThey say my way of doing things is slower, but I think they'll change their tune as soon as they try it.โ€

  2. 2

    To change one's story.

    โ€œThe suspect changed his tune when he learned the police had the evidence.โ€

Source: https://en.wiktionary.org/wiki/change%20one's%20tune