most cases it is that the user has switched off the call forward to v/m
to check this we will need to know
1. what is the model of the phone system
2. dial 165 do you hear the voicemail answer?
if not try 265
if so and the phone system is a KX-TD, Series System from the user handset lift handset and dial 7105165# or 7105265#


Peter (www.vpi.ie)