You can make your own bag, lined with aluminium foil.

Alternatively, buy a silvered "antistatic" bag used for protecting electronic semiconductors. (Not the pink ones, the silvered type.) https://eu.mouser.com/ProductDetail/Desco/13215?qs=sAA9Uk8jJ2hPt7qDCq%252BIQQ%3D%3D

Or simply set the phone to "airplane mode".

You can make your own bag, lined with aluminium foil.

Alternatively, buy a silvered "antistatic" bag used for protecting electronic semiconductors. (Not the pink ones, the silvered type.)

Or simply set the phone to "airplane mode".