Comment: Correct. Your phone can be

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In reply to comment: isn't the bigger problem (see in situ)

Correct. Your phone can be

Correct. Your phone can be tracked and the microphone can be activated without your even realizing it. If you completely remove your battery, this will disable all functionality but iPhones do not allow battery removal because removable batteries can lead to cell phone fires or explosions if they get wet or are tampered with and Apple prefers to maintain control over that aspect of their products. Maybe invest in a Faraday cage?