iPhone ringer
How do I turn the ringer off of my iPhone 12
The left side switch. See: How to put your iPhone on vibrate, ring, or silent mode - Apple Support
Another option: Use Do Not Disturb on your iPhone, iPad, and iPod touch - Apple Support
Of open Control Center by swiping down from the top right of the screen, tap the moon-shaped focus icon, tap the ... to the right of Do Not Disturb, tap "For 1 Hour" or "Until this evening" or "Until I leave this location."