A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
You may let IT to kick the user out of that file.
Go to Computer Management -> System Tools -> Shared Folders -> Open Files to find out who has a document locked. If the user can't be contacted to disconnect themselves, you can forcefully do so by right clicking the locked file and selecting Close Open File
Microsoft Office document is "locked for editing by 'another user'" - Super User