Although it might be surprising for many people, the answer is that your phone can still be tracked even if you turn it off. This is because advanced smartphones are made of systems and subsystems that work independently from your operative system.
With this in mind, knowing whether someone is tracking you can be a challenging thing to notice, even when your phone is turned off. For this reason, we recommend buying a Faraday pouch that will keep your device safe from any type of malicious activity, and you will feel more relaxed knowing that your private data is safe.