How to turn off while iPhone is locked option in do not disturb settings. I am unable to receive calls when my phone is locked.

Those settings are only active when the iPhone Do Not Disturb is turned on. When it is off, that does not affect the iPhone receiving calls. If you are not receiving calls, is it possible these are calls that are not in your Contacts? If so, then go to Settings>Phone>Silence Unknown Callers.

The obvious way to do it would be to unlock your phone and then go to Settings>Do Not Disturb and turn it off. You can turn it off while the phone is locked if you wake up the phone and then tap on the notification, them tap on Turn Off.

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