How can I stop someone from accessing my iPhone Calendar?

I used to have an iPhone 10 over four years ago and I completely wiped it of everything, I have it to my friend cause she was in need of a phone and she’s able to see all of my calendars and notes, is there anyway I can stop her from accessing that ?

[Re-Titled by Moderator]

Original Title: How come others can see my calendar when i did’nt share it