Please make sure you are logged into your Gynzy account. You can then manage your subscription here: https://www.gynzy.com/account/pricing by finding your subscription type and scrolling down to Manage subscription. This button will appear below the subscription you have selected.
You will then see your current plan and your invoice history. You'll be able to renew or cancel your current plan, add and edit your payment method, and update your email and billing addresses.