I hadn’t heard this before. Woud you please give a bit more detail.
Sure, a microwave has blocking for the radar waves which also block your cell phone. I read it somewhere, but if you want to make sure they can’t hear, you can put them in a microwave.
I will have to try to call my cell in a microwave and see if it works.
It does work. The phone never rang. So, if you don’t want to be monitored you know where to store your phone.