can't delete my iCloud back up

I just upgraded my iPhone 4 to the new iPhone 5.  The problem is, I can't get the new phone to back up to iCloud becasue the old one still has a backup on there that's taking up most of the storage space.  I haven't been able to delete the old one becasue it says it's still in use.  I wiped my old phone.  I also tried to delete it from the settings in my Macbook Pro and same issue.  Anyone have this problem?