1 possible fix for now is to check the files in your root>.trash folder.
and select all then delete.
the server may not have purged all the files you think you deleted,
therefore they may still be taking up space on your account.
also delete any backups you might have saved like .zip files.
as your account has no use for those files besides as a temporary thing
intended to be saved to your pc.
this is not a fix to the size limit but it may give temporary access to stuff
until they get fixing your issue.