Question: how to change your password on a nortel phone?
Answer: Go to one of the bigger phones in your office, for example “Nortel T7316E”, or “Nortel T7324”
Press “Feature” -> Enter 983, the screen should show “LOG”, then enter your password then press OK. ... 
Press “MBOX” -> press “CHANGE”, then enter the mailbox number that you want to reset.