You can delete a contact from your own personal directory.
If you have been configured as a system phone user by the system administrator, then you can also add, edit and delete some external directory contacts.
Pressing a key enters all of the characters represented by that key. Pressing another key adds the characters from that button to the previous key press.
For example, dialing 527 matches all names starting with JAS (for example "Jason") and with KAR (for example "Karl") plus any other letter combinations from those 3 key presses. See How the Directory Search Works.
To remove all the characters entered so far, press Clear.