Turn Do Not Disturb on or off
In general, you can suspect that a person that you are trying to Call is using Do Not Disturb Mode, if you observe the following.
If you'd like to allow certain calls to come through while your phone is in Do Not Disturb mode, you can designate this in the feature's settings: Go to Settings > Do Not Disturb > Allow Calls From. Select Everyone, No One, or Favorites; alternatively, select a group.
Deactivate iPhone's Do Not Disturb Mode From Settings On your iPhone, launch the Settings app. Then tap the “Do Not Disturb” option. Turn off the “Do Not Disturb” toggle. Your iPhone's Do Not Disturb mode is now disabled, and you will receive all your calls, alerts, and notifications as usual.
To turn on Do Not Disturb from Control Center: Open Control Center on your iPhone or iPod touch, or on your iPad. Tap Focus, then tap Do Not Disturb.
You access the Do Not Disturb feature in your iPhone's Control Center. The icon for this feature looks like a crescent moon. Simply tapping it turns on the Do Not Disturb feature. To turn the feature off, you just need to tap the icon again.
How to manually use Do Not Disturb on an iPhone
On Android Phones First, open the Settings app and head to Sound > Do Not Disturb.
Turn on Focus If you set up Focus for Fitness, you can automatically silence calls and alerts on your Apple Watch when you begin a workout. Open the Settings app on your Apple Watch. Tap Focus, then tap Fitness. Turn on When starting a workout.
Do Not Disturb During Bedtime is a hidden feature that enables Do Not Disturb mode (which mutes incoming notifications), darkens the Lock screen, and hides all notifications in Notification Center during your Bedtime hours. Of course, the aim is to help you switch off and get a better night's sleep.
Use Do Not Disturb on your Apple iPhone 8 Plus iOS 11.0 Press Settings. Press Do Not Disturb. Press the indicator next to "Do Not Disturb" to turn the function on or off. Press the indicator next to "Scheduled" and follow the instructions on the screen to select the required period for Do Not Disturb.
Apple iPhone - Turn Do Not Disturb On / Off