Once you subscribe to the Call Display feature, you will automatically see your callers’ numbers displayed on your mobile phone screen. You don’t have to do anything to activate the service.
You’ll also see the caller's name displayed if the caller is in your phonebook. And, depending on your mobile phone model, all the numbers of people who call may automatically be stored in a list or log when your phone is on and in a service zone.
If the display reads Restricted, it means the caller has intentionally blocked their number.