When you sign up for a paid subscription, your subscription renews automatically at the end of your billing cycle, and your payment method on your account will be charged automatically. To prevent this, you should downgrade your account before your subscription expires.
As all the charges made to an account are non-refundable according to our "Terms of Service", we unfortunately cannot provide refunds.
This is mentioned in our "Terms of Service" - see section "3. Fees and Payment - Point e. and g.", and is also mentioned when you confirm the payment after adding a service to your account: