AASTRA 6700i series, 9143, 9480i, 9480i CT SIP Administrator Guide EN - Manual (Page 471)

5-194 41-001343-01 Rev 03, Release 3.2.2
7 Click on Operation->Softkeys and XML;
or
Click on Operation->Programmable Keys;
or
Click on Operation->Expansion Module.
Note: If there is no DND key configured or if it is removed, DND is disabled on the IP Phone.
8 Click to save your changes.
Aastra Web UI
Softkeys 1 and 2 configured for DND