How to permanently disable Do Not Disturb on iPhone?

FIRST, if this only occurs for incoming phone calls that has nothing to do with Do Not Disturb→Why doesn't my iPhone ring?

NEXT, if it only occurs when driving, the Driving Focus is set to automatic, which can be controlled by Parental Controls or Mobile Device Management or if your iPhone has a work of school email address.

If it IS Do Not Disturb:

Focus and Do Not Disturb setup has been made much more flexible to meet user demands for additional features, but this has come at the cost of much more complication. To get it working again, do these steps ONCE:

• Tap Settings
• Tap Focus
• Tap on any Focus settings that you will never use and remove them (you can add them back later if you change your mind, and even create new, custom ones)
• Tap Do Not Disturb
• Turn off Intelligent Breakthrough & Silencing (unless you want it after reading the description)
• Tap People
• Tap Allow Notifications From
• If anyone is listed who should not call you when DND is on delete them; if you don’t want any calls from anyone, any time, delete all people
• Tap the dropdown next to Allow Calls From and choose Allowed People Only
• Optionally, tap on Apps, then Allow Notifications From and don’t add any apps.
• Turn off Repeat Calls

All of the above is a one-time setup. After that, turn DND on or off with a quick tap on the Control Center DND button, circled in green below:

You can optionally set one or more schedules by going to:

Settings/Focus/Do Not Disturb/Set a Schedule.

There are many other features, but these instructions put it back to the way it worked in simpler days. Over the years Apple has had a steady stream of requests for DND enhancements, and they seem to have incorporated all of them.

You’re not actually speaking to people that get paid to learn and keep up with Apple changes. Simply fellow Apple users which some are more tech savvy than others.

How long have you had the issue? Not sure why DND would come on randomly (any chance you or someone has screen time restrictions on? Not sure if that would have anything to do with your issue but doesn’t hurt to ask). Or do you have a schedule enabled for one of the DND focus options which would explain why it would seem to come on random (could be triggered by a set time, location, or while using a certain app being set as the schedule).

Have you contacted Apple directly (by phone or at a local Apple Store if you have one in your area) to try and troubleshoot your issue?