I found it -- Page 223 of the V3000 admin guide from 3Com.com (i used 3c10600a to find the manual) Under "Voice Application Set-up utlity" Mailbox 999 or 9999 (3 or 4 digit dial plan) password 0000
The directions below are from a 3Com handset but it would work from any phone in the world just dial in and get to your v-mailbox and then press * to change mailboxes.
Using the Voice Application Setup Utility
From a 3Com telephone, you can use the Auto Attendant Setup Utility.
Follow these steps:
1 Lift the telephone handset, and then press the MSG button to access the
Voice Mail system.
2 At the voice mail password prompt, press *.
3 At the voice mail extension prompt, dial 999 if you are using a 3-digit dial plan or 9999 if you are using a 4-digit dial plan.
4
Enter the Auto Attendant password.
The default password is 0000.
3Com recommends that you change this password.
press 1 to assign actions to dial pad key, 9 to record
greetings, schedules, change password
Follow prompts to assign key pad button actions, record and play back greetings, change the schedule (morning, afternoon, and evening) and change the Auto Attendant password.