Cannot remove iphone backup on icloud
Hello,
Recently I have changed my iPhone (from 5 to 6s). My iPhone 5 was backed up on iCloud (about 1.6Go). Now, I cannot back up my new iPhone because I need more space on iCloud, but the thing is that I cannot remove the backup of my iPhone 5. I have tried using icloud.com, settings of my macbook and settings of my iPhone 6s. I don't have my iPhone 5 anymore.
I called Apple, they told me that they cannot do that (they say I should have done that with my iPhone 5 before selling it)! I can't believe it, my case should be very frequent.
Any idea ?
Thanks
(and sorry for my english...)