If you were charged twice in one month, you might have created 2 separate accounts and registered for PREMIUM memberships with both of them.
In order to resolve this issue, please send an email to help@ondemandkorea.com with the following information:
1. The email address you registered with
2. The last 4 digits of the card you used for payment, the payment amount, and the dates on which you were charged
3. Your full name