Yes, you can! We call this process archiving.
Keep in mind, archiving users will not free up the license they are using but will block access from consuming more modules.
To archive a user, you will go to Admin > Users. You can find the user by using the search. Once you've found who you'd like to archive, you can click the red "Archive" button on the right.
Once a user is archived, they will no longer be able to login to Security Journey. To unarchive a user, you can click the "Restore Button."
*NOTE this will NOT free the user's license until the renewal date