You cannot turn off the iPhone X by holding down the side button. Apple no longer calls the larger button on the side the power button, as it doesn’t actually turn off the iPhone. One press wakes up the iPhone, two presses turn on Apple Pay, and five presses can trigger a call to emergency services, but no hits to hang up. Holding it like turning off other iPhones activates Siri.
Here’s what you need to do to turn off the iPhone X;
Instead of holding this side button, you have to press and hold the volume down button and the side button. After about 2 seconds, you will see a screen with the Slide to power off option as well as the Medical ID and Emergency SOS sliders. Slide the top slide to the right and the iPhone will turn off.
Another option to turn off the iPhone X is to go to.
There is no way to use Siri to turn off your iPhone X. Perhaps we will see Apple add this to the iPhone software in a future update.
Press and hold the side button for a second or two to turn iPhone X back on. You will see an Apple logo and the iPhone X will boot up. You can also plug in a lightning cable to charge the iPhone X that turns on.
If your iPhone X is frozen, you need to volume up, volume down and then press and hold the side button for about 10 seconds. This will force restart the iPhone X.