Can't delete old iCloud backup
Had a phone set up to back up to iCloud. That phone went dead, and was returned to Apple and exchanged with a new one. Because the screen went dead -- thus rendering the phone inoperable -- I was unable to shut off iCloud backups and delete the old backup.
Right now, I can't delete the old phone's iCloud backup, and I don't have enough space to start backups on the replacement phone. How can I resolve this?