You can use DND to reject incoming calls automatically on the phone. Callers will receive a busy message.  

You can receive incoming calls from authorized numbers when DND is enabled.  

To configure the DND mode via web user interface:  

1. Click on Features->Forward & DND.

2. In the DND block, mark the desired radio box in the Mode field. 

3. Click Confirm to accept the change.

To activate DND in phone mode: 

1. Press the DND soft key when the phone is idle.

The  icon on the idle screen indicates that DND is enabled.

Incoming calls will be rejected automatically and "n New Missed Call(s)" ("n"  indicates the number of the missed calls) will appear on the LCD screen.