With Focus in iOS 15 and iPadOS 15 or later, you can use Do Not Disturb to mute calls, alerts, and notifications you receive when your device is locked . You can also program Do Not Disturb and allow calls from certain people.

When Do Not Disturb is turned on, a crescent moon icon appears in the status bar and on your lock screen.

To turn on Do Not Disturb in Control Center:

If you don’t want to be disturbed at a specific time, you can schedule Do Not Disturb and change its settings to concentrate.

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Why does my do not disturb mode keep turning on?