flashing call indicator lamp - NEC IP4WW SL1100

We have the NEC SL1100 IP4WW models and one extension has a permanent fast flashing green light at the top.  I under it is the 'Call indicator lamp' .  Please could anyone advise how to stop it flashing.  Many thanks
emma sAsked:
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WakeupSpecialist 1Commented:
To cancel all your Messages Waiting:
Note: This includes messages you have left for other extensions and
 messages other extension have left for you.
 1. Press the Speaker key.
 2. Dial 773.
 3. Hang up.
 To cancel the Messages Waiting you have left at a specific extension:
 1. Press the Speaker key.
 2. Dial 771.
 3. Dial number of extension you do not want to have your messages.
 4. Hang up.
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