Why can’t I be able to update my iOS version to iOS 14.0
Why can’t I be able to update my iOS version to iOS 14.0
iPhone 7, iOS 13
Assuming you have a compatible device, you can update to iOS 15.6, 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.