To turn off SOS on an iPhone, follow these steps:

1. Open the Settings app on your iPhone.
2. Scroll down and tap on "Emergency SOS."
3. Toggle off the options such as "Call with Hold and Release," "Call with 5 Button Presses," and if available, "Call After Serious Crash." This will disable the automatic SOS calling features.
4. You can also use Siri to turn off Emergency SOS by saying, "Hey Siri, turn off Emergency SOS."

These steps prevent the SOS feature from being accidentally triggered while still allowing manual activation if needed. However, it's generally recommended to keep Emergency SOS enabled for safety reasons unless accidental activations are a concern.