If the Block Incoming Calls feature is enabled by your administrator and the phone is locked, you cannot answer incoming calls. The phone will:
Play an alert tone and flash the beacon LED to indicate an incoming call, without displaying the incoming call popup on the phone display.
Default any custom ringtone to the generic ringtone.
Log missed calls in the Recents application and mark them with a missed call icon.
When you dial an emergency number, the incoming calls on the primary, bridged and shared call appearances buttons do not display the caller details.
When you unlock the phone, the incoming call popup displays with caller details, allowing you to answer the call as usual.