nostr:npub1xd3kd9vvvudk2qzcnqjr9w0x878vf9qwju3mwu3w2m40tasz986qka9tk9 nostr:npub1h05h8cffeptypv8pe2vn8rd0yrah0t92lzwnz6x776ghrlsvpulqccshrl 
The only way to ensure your phone is truly off is removing the battery. However I not so exactly sure if that is true. I know of ways using a small capacitor that holds a charge, and when it receives a Certain signal from a tower, it energizes a circuit long enough to perform a function. It has to be quick though it can't provide power for very long. Unless they have tapped into some Tesla technology. Think of those chargers you just lay your phone with without plugging.