How do I turn the Alarm off on my iPhone 6?

Was that consistent over many days?

Anyways, how about if you just delete that odd alarm altogether - by hitting the Edit button first in that view? Alarms are easy to set up anew anyway.

BTW, maybe the iPhone community would be a better home for this question?

If the alarms come back from nowhere, I would unpair and pair again. That behaviour is not normal and something in your setup seem broken. Repairing hopefully fixes it.

Set up and pair your Apple Watch with iPhone - Apple Support