I have gotten mixed results.

In Y - "If it's on it will be on channel 9"
In F - "I'll call the captain and ask him for you"

At one point on a FRA-ORD flight in F, it was turned off mid flight. I made a comment to the FA that they turned it off. She walked up to the galley and called the captain. A few moments later she returned back to my seat and said "It's back on again"