You are going to need to speak with your voicemail administrator on this one. The initial password for voicemail enrollment is usually different for each user (for security reasons). There could also be other issues in play here that are preventing voicemail first time enrollment.
Yes, as Rob says you need to contact the IT department and tell them to reset the password to what your co-workers want, it is done on the System Administrator (SaWeb) page from the Unity server, first you search for the Subscriber then on the left options you go to Phone Password.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.