A Microsoft file hosting and synchronization service.
Hello, thank you for reaching out to Microsoft Q&A.
Do you have the OneDrive app installed on your iPhone? If yes, just open the app and select your profile picture in the top left corner.
Go to Settings > Camera Backup, then turn off the toggle for your Microsoft account.
This should stop the iPhone photos from automatically backing up to your OneDrive Storage
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To free up your Microsoft Storage space:
Open an incognito tab on any web browser and sign in with your Microsoft account here-
https://onedrive.live.com/?v=managestorage
Where you see "free up space," select OneDrive.
So, this will redirect you to the "Largest files in your OneDrive" page.
Select the file you no longer want on OneDrive and click Delete.
Ensure you delete them from the recycle bin folder as well.
Important - Ensure you have a backup of the file before deleting it from OneDrive.