Nortel Voicemail Problems

I have a customer who uses a Nortel Norstar phone system and voicemail
package.

I have come across a problem where the user dials in to voicemail from
outside the company, but is told there are no messages waiting, even
though we know there are. The user has apparently conencted to the
correct mailbox (changing passwords confirmed this) but is not
recieving messages.

The only thing that is leaping out at me is that the mailbox ID is 21,
but when we try to program the ext to be 21 (using Feat. 983) the
comment comes back "Ext Assigned". There are only 3 mailboxes on the
system and none of them appear to have that extension assigned if I
browse through them.

Any advice would eb greatfully accepted.

Thank you.

.