I have a Mitel Superset Phone 4025 and the display screen says Messages Phonebook and there are no messages.

Some 4025 supersets have back lit displays and some don't you may have the model that does not light.

The Message Waiting Indicator lamp on the Mitel SS4025 is set and cleared by the main system controller (back room equipment) and is further dependent on the integration between the system controller and the voice mail server. Depending on the type (age) of Mitel main control, the voice mail could be built-in to the Mitel system itself or a separate stand alone server, such as an Octel (Avaya) system. In any event this problem needs to be reported to your phone system maintenance person. Any competent Mitel System tech should be able to resolve the problem for you quickly.

You have unheard messages on the voicemail system provided by your telephone company. This system records messages when someone calls while you're already on the phone. Please contact your telephone company for instructions on accessing their voicemail system.

Try to restart the phone. Unplug it for 10 minute and then start it normally...
try this and let me know

it's because the operator set a message to your phone. You need to leave the handset on the cradle and push the message button. Read the display and follow the prompts. You should be able to clear the message.

What sort of messages? I think you are referencing Status messages. If so, you are also referring to either SX2000 or 3300ICP. The Status Messages are defined in the system programming by your system administrator or vendor.

Hi,
Visit to the given link and download the manual... this manual contents the information required by you...
http://www.retrevo.com/support/Mitel-4025-Telephones-manual/id/3040ci572/t/2/
Hope this has helped you... Thanks...

You should contact your vendor for this support.

Phonebook is for internal extensions. As soon as you add a ext. and name in phone system it is added to the phonebook.

It depends on your Mitel Telephone system.

If your system is an SX200 ICP ~ then going thru the Blue Superkey options the Mitel will let you change your own name.

But ~ if you have a 3300 ICP then the name change is only performed via the system programming.