I'm using 7910 IP phones in meeting rooms, so they don't need to have voice mail configured.
The problem that I have, I need to power off the led of voice mail, this led is always power on.
Do you know how I can power the led off ?.
Give this a try.
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!