Q: "ghost" files keep using iCloud space, but Library is empty

Problem: iCloud storage says that I have 3.3 GB (from 5GB) used by photos and videos.

Facts:

- I have no photos or videos stored in iCloud. I already deleted all of them. Both iPhone and Photos app says that my Library is empty.

- I already deleted "Recently deleted" folder.

- I already formated my iPhone to factory settings (deleting all the content)

- I already deleted backups from my iPhone.

I don't understand how I can free up my space. And destroy this "gost:" files once for all.

Thanks

-Mario