To turn off Do Not Disturb on an iPhone, follow these steps:

• Open the Control Center:
  • On iPhone X and later, swipe down from the top-right corner of the screen.
  • On earlier models, swipe up from the bottom of the screen.
• Tap the Do Not Disturb icon, which looks like a crescent moon. If Do Not Disturb is on, the icon will be highlighted; tapping it will turn it off and remove the moon icon from the status bar

Additionally, to prevent Do Not Disturb from turning on automatically at scheduled times:

• Go to Settings > Focus > Do Not Disturb.
• Turn off the Scheduled option under the schedule settings

This will fully disable Do Not Disturb until you manually turn it back on.