Ghost alarm on iPhone 12 every Saturday morning

My girlfriends iPhone sets off a ghostalarm early every Saturday morning. And with an alarm/ringtone that does not even exist in the iPhone library. It's been going on for years and it's starting to become really annoying.

She has upgraded her phone from a 7 to iPhone 12 once since this started but that didn't help.

We have checked every app on her phone to see if there could be some app with a calander/alarm function but could't find anything. The spooky thing is the alarmtone like I said, it's not even in the iphone library! It's a pianopiece lol!

Any ideas? Thanks.

[Re-Titled By Moderator]