Delete backup sets created on old computer using Norton 360

Over the years, I have created numerous online backup sets using Norton 360 or Norton Online Backup on computers I no longer use.  These backup sets remain linked to my Norton account and use up space on Norton's servers I need for new backups.  There does not seem to be any clear way to log into my Norton account and remove these old backup sets from Norton's servers.  (I currently use 360 for backups, but no longer subscribe to Norton Online Backup and no longer have the computers I used to create the old online backup sets I want to delete.)  An search of this issue discovers multiple complaints/questions about this issue, but no solutions that fit my situation.  Help would be appreciated.