Closed user group (Menu 4-4-3)
This network service specifies the group of people to whom you can
call and who can call you.
Preset
resets the phone to use a user
group that the SIM card owner has agreed upon with the service
provider.
NOTE: When calls are limited to Closed User Groups, calls
may be possible to certain emergency numbers in some
networks (e.g. 112, 911 or other official emergency
number).