As a reseller, you have control over your customers' access to data.
You can set a Company to 4 different statuses in the reseller administration panel:
Active This is the normal state where everything works, and users can login.
Suspended This is a soft way to limit the users: they can still login and read and download their data, but cannot upload.
Deactivated This is a harder way to limit the users: they can still login and read the files they have downloaded, but cannot download or upload new files.
Deleted The company can no longer be seen in any panel, and users cannot login to it, nor access any data on it.