You can use the Status menu to switch off 'do not disturb.'

1.Press the Status soft key if shown.
To access the Status menu during a call, press the key phone PHONE key and then press the Status soft key if shown.
2.If necessary use the up arrow up and down down arrow arrow keys to highlight Do Not Disturb.
To clear the 'do not disturb' setting, press the Off soft key.

Access Control

Your system administrator can configure whether you can access this menu option. See Menu Access Control.