If your phone based on Windows Mobile (or Windows Phone) will notify one or more unread voicemail and you can not listen or want to cancel the notification, you can still remove it with the following instructions.
From the registry of the device (available with software such as PHM Registry Editor ) go to the key
WM 6.0 HKLM \ System \ State \ Shell \ Vmail \
WM 6.5 HKLM \ System \ State \ Messages \ Vmail \
From here to access the subkeys Line [x] (where [x] there will be a number, as Line1, Line2, etc.), and Total Count in the key and delete each subkey (eg HKLM \ System \ State \ Shell \ vmail \ Line1).
Then wipe out the key text (which contains the text of the notification)
April 16, 2010 14:44
It works just the way as far as my wm6.5 is: \ HKLM \ system \ been \ messages \ vmail
April 16, 2010 14:57
Thanks for the update, I proceeded to edit the article.
January 9, 2011 19:59
Thanks, very helpful.