Is there a way for phone users to manually turn of the MWI light if they know there are no messages?
Just to add a note to the good tip from my friend Marwan.
To find the MWI - OFF DN (just in case :)
In CCM look up the MW-Off number (Feature>Voicemail>Message Waiting>Directory Number>Message Waiting Indicator Off )
This will be a Directory Number like perhaps 2600. Go to the phone, press the Line button, dial 2600 and the MWI Lamp/Icon and Message will turn off.
Hope this helps!