Memberships are not auto-renewing. So you don't need to cancel anything to stop future charges as there are no future charges.
Refunds: You can request a refund within the first 5% days of your membership's duration.:
30 Days membership: Cancel within 2 days of subscription.
90 Days membership: Cancel within 4 days of subscription.
6 Months membership: Cancel within 10 days of subscription.
1 Year membership: Cancel within 20 days of subscription.