No off button on this system or Mazda connect. You can turn the volume down on the radio and nav/phone alerts will still come through though. Each "app" or section or whatever has its own volume level.
I purchased Toyota Yaris iA last week.
I am also struggling to find a button or control to turn radio off after I switched it ON.
Is n't this silly ? In today's world of digital automation, why such basic feature is not provided by car companies ?