sing a different tune / song

/sˈɪŋ ɐ dˈɪfɹənt tjˈuːn sˈɒŋ/

/sˈɪŋ ɐ dˈɪfɹənt tˈuːn sˈɔŋ/

to sing a different tune / song

to talk or act differently because of a change in opinion, behavior, or attitude, especially one that happens abruptly