I need to delete all voice messages in a voice box. I deleted all items in Inbox folder for the user but ip phone still show "you have new voice messages" message.
I use Unity 4.0
To remove the on screen message "you have new voice messages" just dial the MWI-Off directory number from the phone itself.
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!