You can have the phonebook etc set to either personal or common with common being the default.
It seems to me that you have at least one of them set to personal.
If you have a mark II handset the press OK and turn the dial to SETTINGS then press OK
Now turn the dial to HANDSET and press OK
Now turn the dial to COMMON and press OK
Changing a handset from personal to common causes the personal Phonebook, Caller ID and Redial list to be replaced, NOT supplemented, by the common lists. Updating the Phonebook, Caller ID and Redial lists may take a few minutes.