I want to update my phone to the latest version

To update to the most recent, compatibile version, please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support If the above Apple articles do not help, please post back with relevant information. 

If your tag line is correct and you own iPhone X on iOS 16, iOS 16 is the highest version an iPhone X can run. If you were hoping to update to iOS 17, that won't be possible.