Subscriptions can be canceled at any time during the subscription period up until 24 hours before its renewal, however, refunds for the purchased Subscription models cannot be provided at all times.
Refunds for Monthly Subscription are not available and that model can only be canceled so it is not renewed upon the end of the one month period.
The yearly Subscription can be canceled and refunded 30 days from purchase.
On more information on how to cancel the Subscription, please refer to this article How can I cancel my Subscription.