Hello greffin33,
We definitely want to make sure that all of your lines have the voice mail option available and set up. No one wants to miss any important calls by not having a voice mail box set up. It sounds like he is missing the voice mail box on his number. That is really an easy fix. Have you tried contacting Customer Care? Please Contact Us when you have a minute and we can get that voice mail box added to his number.
Thank you!
Alissa