I have DTerm80 phone and it has former employee passcode programmed in. I need to change the passcode so I can listen to messages and change the greeting.

SOURCE: samsung idcs 18d password

To change a voice mail password you would need to contact the service provider and explain the situation and they will reset the code. You may need to visit the provider directly as they may require valid identification.

SOURCE: Trying to change the name on a phone

1. Press FEATURE * * 2 6 6 3 4 4
2. Enter Password: 2 6 6 3 4 4
3.Press the top grey button (the set on the lower right hand side with the grey buttons closest together)
4. press the button under the one you just pushed until you get the desired name/ or the one with no name
5.press the same button as in number 3 (once only)
6.press the same button as in number 4 (2 times) you should get the name and a soft key button for change
7.type the name like a text message
8. once you filled it in hit the same button as in number 4.
9. hit release

SOURCE: changing employee name on extension

http://www.phonserv.com/1_m7310_phone_meridian_norstar_phone_system.htm

This has PDF file that will give instructions.

Also this link has more instructions:
http://www.phonserv.com/1_PDF_user_guide_meridian_norstar_phone_systems.htm

To Change the Name on a Mailbox:
1. Log into system administration
2. Select the softkey under "MBOX"
3. Select the softkey under "Chng"
4. Enter the mailbox number (extension. you want to change the name on
5. The display shows "Reset Password"
6. Select the softkey under "Next", keep hitting "Next" until the display shows the name
7. Select the softkey under "Chng" to enter a new name
8. Enter the name using the dial pad. Enter last name first, press "# #" to enter a comma and then enter the first name. When spelling the name, press "#" to move to the next character
9. Select the softkey under "Next" to save the change
10. Hit the release button

SOURCE: A former employee changed the viocemail password

call your provider and have them reset it. it may also be an option when you try to call voicemail

SOURCE: Main greeting

When you log into the voicemail, what does the lady say?

Welcome to Merlin mail, merlin messaging, Audix???

Need to know the voicemail model....