switch something on
phrasal verb with switch verb [ T, I usually + adv/prep ] uk/swɪtʃ/ us/swɪtʃ/
usually disapproving
（通常不是发自内心地）突然变得，突然装出
If someone switches on a particular emotion or behaviour, they suddenly start to feel or behave in that way, but usually not sincerely.
When a customer walks in, she switches on the charm. 一有顾客走进来，她就马上装出亲切可人的样子。