sign (something) off
phrasal verb with sign verb uk/saɪn/ us/saɪn/
结束（写信、广播或电视节目）
to give a final message at the end of a letter or when communicating by radio, or at the end of a television or radio programme
She signed off (her show) by wishing her listeners a Happy New Year. 她在结束播音时祝听众新年快乐。