Do Not Disturb is a feature that, when activated, allows you to automatically send calls to voicemail. The Do Not Disturb button is generally in the bottom, left hand corner of the screen, but your button placement may vary. The Button looks like the example below:

To enable Do Not Disturb, press the feature button next to the label Do Not Disturb.

When the feature button is Green, Do Not Disturb is active and all calls will be sent directly to Voicemail.	When the feature button is Red, your phone will ring like normal!