Mr. Latimer:
Simply as a departure point for thought: I placed my wife’s cell phone inside an empty metal coffee can and covered the open top with aluminum foil. I secured that by overlaying the plastic lid. The phone did not ring, nor would it receive a text. Outside of the can, both calls and texts went through. Should you (we) have a cell phone that has a integrated battery, this may make tracking or malicious communications more difficult. – Skyrat