You may upgrade at any time that suits you and our system will calculate the upgraded on a pro-rated basis and credit you towards the upgrade automatically. Our system calculates the remaining credit on a daily basis so for instance if you subscribed to a package today and used it for a couple of days and then decided to upgrade on the third day, our system will credit you for the remaining 28 days towards the package you are upgrading to. The credit applies regardless of the length of package that you may consider upgrading to.