If you have database programming, go to VOICE PROCESSOR/DEVICES/<mbox numberr>, right-click in PASSWORD area.
Or if you know the vmail admin mailbox and password (where you'd go to record system greetings) you can change his pass by phone. Just log into the admin mbox (you're in the right place if it tells you how full the HDD is). Press 9 for admin options, 2 for mbox and group list maintenance, then enter mbox number. Once in, 3choice changes password.