Have you looked to see if this phone is associated with a hunt group or anything else that has VM?
Also, if you are stumped with this you can pull a VM diagnostic file and search through it.
(From MOL)
To troubleshoot what is initiating the MWI on, obtain diag.dat or diag.sav from either
a> the system diagnostic report logs; or
b> ftp into the controller and manually get the diag.dat file from /vmail/c/voxdrv.
e.g. ftp into controller IP
Type cd /vmail/c/voxdrv
Type get diag.dat
Type get diag.sav
Type bye.
Review Diag.dat or Diag.sav with Notepad or similar application
-Open up the diag.dat in Notepad and search for 3 a.m.
- Look for your MWI On code and mark down all extensions or numbers that the MWI is being set on.
You may find a system speed dial or hunt group number that has an association to the extension that is complaining about the MWI every morning. This could mean you have a vmail box that is associated with the system speed dial that points to the extension, or a hunt group that this DN is the first member of.
Resolution: Change programming I.E MailBox 0=system speed call to the DN that has MWI on in A.M means you have a new voicemail message in the dial 0 mailbox.