Siemens 600 Series - Manual (Page 158)

7–20 ROLMphone 300/600 User Guide
To deactivate
your PIN ➩ Get a dial tone.
➩ Dial * # 5 8.
You will hear the confirmation tone. If you
have a display telephone, IDENTIFICATION
DELETED is displayed.
➩ Hang up.
Note
Do not deactivate your PIN during a call, since this
will disconnect the call.