It is easy to cancel your account, just go to the YOUR SUBSCRIPTION section, scroll down and look for the "cancel service & delete data" button,
( cancellation of account will automatically submit the remaining unused balance for refund to your card )
When you click the "cancel service" button you will first see a pop up window asking you to confirm before continuing, just click ok and the cancel account screen will show,
Click the little check box to confirm and then click the red "Cancel Service Now" button. Once you cancel all data will be deleted and your unused balance will be submitted for a refund.