Game sound turn back on when switch app

Hi everyone i have a problem here.

In my game i have tutorial menu that can turn on/off sound for game.
When it set to off the sound is off but when i app switch while on the game and switch back to the game.
the sound just turning back on but in the option it still setting off.

On the performing a fast app switch i.e. moving away from the game and returning to it,the game background music starts to play,even when the "sound" option is OFF

anyone how to fix this