If you already have a Premium Subscription and you want to upgrade it, you have to:
1. Go to the "More" tab.
2. Tap on the "Store" menu option.
3. Choose one of the available options and tap on "Upgrade".
4. Tap the "Continue" button.
Note: If you upgrade your Subscription, the new Subscription will begin instantly, canceling the old one. The price of the Subscription may vary according to your location.
How do I subscribe?
How do I manage my Subscription?