If your subscription is managed via Stripe, please visit this link. Submit using the email address that you used to sign up for the subscription, and you should be able to cancel the subscription from there.
If your subscription is managed via PayPal, you will need to log in to your PayPal account. Navigate to your "My preapproved payments" page. Under "Merchant" column select and click on the relevant merchant. In the merchant billing page, select "Cancel" to cancel the subscription profile.
Be warned that after you cancelled, your site will not be accessible immediately after that. Please ensure that you have backup or exported your apps before cancelling.