To change your package, go into Skipta um pakka from the menu. You have the option to cancel your current subscription or switch to another one. If you choose to upgrade your subscription, the changes will take place immediately and you will also receive a refund on the remaining days of your previous subscription. If you choose to downgrade to a smaller package, the change will take place on your next billing date.
If you pay through iTunes, all changes must be made through them. You must cancel your package and wait until it’s no active anymore before you can start a new one. Learn more about unsubscribing through iTunes here.