Open command prompt as administrator and type below commands
list volume (here is now seen which volume has letter)
select volume x (x is a volume number when you want remove)
remove letter=x (x is a selected volume letters)
Open a Command Prompt (with Admin)
subst x: /d ( where X: is the drive letter of the phantom drive. )
Also, Please check if there is any GPO which is configured to mount shared folders for the users.
--If the reply is helpful, please Upvote and Accept as answer--