Click on the DND button which is just below the LCD screen. See screenshot below:
On some models you will not be able to do this via the LCD main screen and will need to go into the menu settings instead:
Enabling Do Not Disturb
- On your phone, press the Menu button
- Select Features > DND
- Use your arrow keys to select the Phone Mode from the Username field
- Select Enable from the DND field
- Press OK to accept the change
- The DND icon on the idle screen indicates that the Do Not Disturb mode is enabled.
Incoming calls will be rejected automatically and "n Missed Call" ("n" indicates the
number of the missed calls) will prompt on the LCD screen.
Disabling Do Not Disturb
- On your phone, press the Menu button
- Select Features > DND
- Use your arrow keys to select the Phone Mode from the Username field
- Select Disable from the DND field
- Press OK to accept the change