You can get Refund for you iCloud Storage Space within 15 Days of your Upgrade as mentioned below.
You need to Contact Apple Support : http://support.apple.com/kb/he57
Or you can also click on iCloud Support Highlighted below and then continue choosing the exact option to contact Apple.
- If you need more iCloud storage, you can purchase additional iCloud storage from your iOS device, Mac, or PC. See iCloud storage plan overview.
- If you find that you do not need the additional storage you purchased, see iCloud: Storage upgrades and downgrades for steps to downgrade your storage.
- For a full refund, contact iCloud Support within 15 days of an upgrade or within 45 days after a yearly payment. Partial refunds are available where required by law.
- See iCloud: Storage and backup overview for more information about what iCloud backs up.
- See troubleshooting storage issues for more information.
- See iCloud system requirements for more information.