Someone just brought an iPhone to me which was missing an icon for the phone on the home screen!    Now obviously this reduces the functionality of the device as a phone somewhat!

Turns out there’s an easy fix though:

Go into Settings, General, then “Reset Home Screen Layout”

You should now have a working phone icon again!

Update: Several reports suggest checking Settings, General, Restrictions as this may also disable the phone icon.   More details on restrictions here:

Update 2: Another tip reported – double tap the home button and look for the icon in the tray at the bottom of the screen.   You can then drag it back from there.