Yes, a discount of the unused portion of your current subscription will be automatically applied when you upgrade your subscription.
As the system is automated, the subscription periods are set to 3 months or 12 months and do not allow for a cash refund, only a redirection of the unused portion of your current subscription to an upgrade.
For example, if you purchased the Basic version for the year (US$29) and then the next day decided to upgrade to the Standard version for 3 months (US$99) it would only cost US$70 (99-29) to upgrade.
You can buy monthly subscriptions via the App stores, but the most economical way of purchasing a subscription is direct from our website, where you can buy a 3 monthly or yearly subscription.