Related to Do Not Disturb turning on, do you have any wallpapers assigned to a focus mode? When you hold down on the lock screen (when the iPhone is unlocked), it should let you change your wallpaper. A wallpaper can be set to a focus mode to let you have different wallpapers change when a focus is turned on. When you switch to the wallpaper, it also turns on that focus mode. Turning off the focus changes the wallpaper. (Kind of annoying if you want one wallpaper for multiple focus modes. You have to make a duplicate wallpaper to use with a different focus mode.) In the chance that you have only one wallpaper and it was set to a focus mode, it may prevent you from turning Do Not Disturb off. Not a common case but thought I would mention it. Maybe it'll help.
In terms of turning Do Not Disturb off, here's the ways I know to turn it off. Maybe one way will work for you while your phone is in this funk.
- Open Control Center from the top right of the screen, tap on the colored focus icon to turn it off (colored means it's on).
- On the lock screen, the focus mode should show up on the bottom of the screen. When the iPhone is unlocked, you should be able to hold shortly on the focus mode and bring up a list of your focus modes. Tap on the mode that is currently on to turn it off. Here's Apple's guide.
- Tell Siri to turn off the focus mode. You need to specifically tell Siri the name of the focus mode that's turned on. Here's an example: "Hey Siri, turn off my Work focus mode."
- Use a Siri Shortcut. This can get really complicated and take too much writing here, so here's a guide on Siri Shortcuts. YouTube is also a great tool for learning how to make Siri Shortcuts.
If these still don't let you turn off Do Not Disturb, you can follow what was done in this community post. Open Control Center, hold down on the Focus button until the list of focus modes shows up. Tap on the three dots next to a focus mode. Tap on one of the schedule options, such as "For 1 hour" to schedule the focus. This may be able to reset the scheduling problem that seems to be occurring.