Personally, I would like to change to include both name and number. This would let me call back easily from a text message.
I know how to do it, but changing files under freepbx is always a bad idea.
This would be handled in the voicemail module for FreePBX. Please open up a feature request http://www.freepbx.org/trac/newticket and we can take a look at it.
Thanks! I was looking around more and found it to already be there in the VM Admin - settings menu. Sorry for the false alarm.