unable to cancel the notification of wireless network I'm using I-phone 6s, today i suddenly found a notification box showing "select a wireless network" when i reached my office. I can't see any networks and at the bottom there is CANCEL option but its not cancelling. please help me out in cancelling it as iam not able to do anything(including switch off or attending calls) thanks.
Force restart the device by pressing and holding the home button  and the sleep/wake button until the screen is black, then let go. When the phone restarts, open settings and go to the Wi-Fi one and disable "Ask to Join Networks".