If you notice your iphone touch screen not working right after installing iOS, it’s likely a software "hang" or a glitch in the new code. Updates can sometimes leave behind temporary files that conflict with the touch drivers. The best way to resolve this is to perform a "hard reboot" to clear the temporary cache. If the screen is partially responsive, ensure all your apps are updated, as an old app running in the background can sometimes cause the entire interface to lag. If it remains completely frozen, connecting it to a computer to "Reinstall" the update via recovery mode is often the fix.