Seriously, it's my understanding that cell phones, even when turned off, continue to ping cell towers. Once, whilst driving across Florida I received a promotional call on my cell phone that was turned off. I had crossed from one company's service area to another and the new company wanted to sell me a subscription to their service. This was a couple decades ago, before smart phones and today's battery technology. I had my phone off to conserve the battery in case of need. That was the first experience I had with phones turned off still pinging cell towers. Since then, I've read that cell phones without SIM cards also ping cell towers. I was never able to find out if this occurs with the phone off or if it must be turned on. I learned of this because old cell phones without SIM cards are donated to women's shelters where they are given to women at risk of battery so that the phones can be used to call 911 (or whatever the local emergency number is). With no SIM card phones will still call the local emergency service, and I think they still ping the towers. I'm pretty sure 911 use without a SIM card or subscribed service is a statutory requirement in the States.
I am of the opinion that cell phones should, by law, have the option to turn off tower pinging, especially smart phones that can use apps. Law enforcement would probably resist that change because they use records of what towers successfully ping phones to track people's whereabouts. I argue that most criminals are too stupid to turn their phones off to avoid being tracked, and honest people should not be burdened with presumptive guilt to make life easier for law enforcement.
