The do not disturb feature (referred to as DND) is used for sending callers directly to voicemail. Reasons to use it may include when you're in a meeting, working and you don't want to be interrupted, going to lunch, or going home at the end of the day.
When do not disturb is enabled, callers are sent directly to voicemail and have the option to leave you a message. If your mailbox is set up with an escape-to-operator option, callers can press 0 and they will be transferred to another person. When do not disturb is enabled, your phone will not ring.
To turn on DND:
Your phone shows you're in DND mode in two ways. The handset with a red circle with a white line icon indicates your phone is in DND mode. Also, the DND mode shows in the status bar at the top of your phone.
When you no longer need DND, you'll need to disable it.
To turn off DND:
The handset icon no longer shows a red circle with a white line, and the status bar at the top of your display will show DND is no longer enabled.