By default Cisco Unity Express only reports the called number in your message for internal calls.
It’s quite simple to change this so that all calls (where a number is available) have their numbers reported.
Router# service-module service-enable 1/0 session
Trying 192.168.n.2, 2066 … Open
se-192-168-n-2#
se-192-168-n-2# conf t
se-192-168-n-2(config)# voicemail callerid
se-192-168-n-2(config)# end
se-192-168-n-2# wr mem
se-192.168-n-2# exit

Session closed

[Connection to 192.168.n.2 closed by [...]

We have two CME’s and a single shared CUE.
Dialplan
CME1:
3002 – Phone 1
3003 – Phone 2
3200 – AA Script (outside scope)
3600 – Voicemail
3998 – MWI off
3999 – MWI on
CME2:
3004 – Phone 1
3005 – Phone 2
3998 – MWI off
3999 – MWI on
on CME1 (Central)
voice service voip
allow-connections sip to h323
allow-connections h323 to sip
allow-connections h323 to h323

interface FastEthernet 0/0
ip [...]

To restore factory defaults on Cisco Unity Express firstly take the module offline by typing “offline“, then when confirmed issue the “restore factory defaults” command.
An example follows :
Router# service-mode  service-engine 1/0
Trying 192.168.n.3, 2006 … Open
se-192-168-n-3# offline
!!!WARNING!!!: If you are going offline to do a backup, it is recommended
that you save the current running configuration using [...]