We hate to see you go, but you can cancel your subscription by clicking an in-app link.
Head to your Account Settings (the wrench icon in the upper right).
Next, select Account Settings and then Subscription from the sidebar on the left.
In the "Current Subscription" section, click the Cancel your subscription here link to start the cancellation process.
Please consider leaving us a note to let us know why you are cancelling, and what we can do to improve ShipStation.