I've been advocating RF-blocking Faraday bags/pouches for cell phones for a long time. Hint: they are still available for purchase on line. Invest in one before they are banned. I actually use two, a smaller one fitting inside a larger one.
And if you can’t get one, Weird Al was prescient.
Aluminum foil layers folded into a bag actually work, too.
I think you might as well bite the bullet and get rid of the phone. You have to find out what it is you really need the phone for, and get alternatives - while you can.
I don’t really see the bag working. You can’t control the phone and never could. People saying “Turn off such-and-such” don’t know what they’re talking about. The phone can tell you that anything is “off” that it wants to, even while still using it. It can record anything, too. If it “heard” or “saw” it in the bag, it can report it later.
The bag or box or battery-removal will surely stop it - while it is in that state. It’s kind of like not having the phone, at all. The phone can report its little black-out periods, too, and I am sure that there are those that would be interested.
Just something to think about.