No one can access their Voice Mail. Everytime the programmed Voicemail button is pressed it prompts 107:V-mail. Not allowing each person to get into their VM. I thought i could log into the system managers mailbox, and re assign the Voice mail boxes. But it won't let me... any ideas as to what could have happened and what can fix this?

Lands Phones - Panasonic - KX-T7731 Corded Phone