Alarm clock

You may have each of the three alarms set differently in the Clock App.

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As an option: The alarms can be set to repeat, or to snooze, or not.

If not set to repeat or snooze, you may not need to turn an alarm off.

More info:

How to set and change alarms on your iPhone - Apple Support

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More info. if you wish to browse:

Other alerts on iPhone:

You may also have set an alert, (eg: for an event in the calendar app), and may not need to turn that off, like you do with an alarm that is set to repeat or snooze.

Create and edit events in Calendar on iPhone – Apple Support

In the Reminders app, reminders can also be set to give an alert.

Use Reminders on your iPhone, iPad, or iPod touch - Apple Support

Then there are notifications that can be set as alerts

Use notifications on your iPhone or iPad - Apple Support

and, you can often choose different sounds for different alerts etc.

How to: Change iPhone sounds and vibrations – Apple Support

All the best :-)

In case you or anyone else is having a similar problem, try going into your phone settings > Face ID and Passcode > uncheck Attention Aware Features.

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