Viki Pass subscriptions will be charged immediately upon confirmation of purchase.
For subscriptions made via the iOS or Android Viki app, iTunes/Google Play will automatically renew your subscription within 24 hours prior to the end of the current subscription period. You may disable the auto-renewal at any time by canceling your subscription before your current cycle end date. To view your subscription cycle dates or cancel your subscription, refer to the Viki Pass section under the app settings or follow the steps listed here.
If you have received a cancelation confirmation from Viki but you're still seeing charges on your bank statement, it's likely that you may have another active subscription. Do refer to this article for more information.