367 Views 1 Reply Latest reply: Dec 27, 2013 3:36 PM by David Menzel
Apple will handle it automatically, so you do not have to to do anything...
If you purchase a higher-tier storage plan for your iCloud account to replace your existing storage plan (for example, a 20 GB plan to replace a 10 GB plan), the existing plan will be canceled and you will receive a prorated refund for the time remaining. The new storage plan is applied to your iCloud account and the annual payment date is updated to reflect the purchase date for the new plan
Please see also: http://support.apple.com/kb/HT4874?viewlocale=en_US&locale=en_US