How do I downgrade to a lesser plan on your app?

Downgrading from your current plan is a straightforward process. It follows the same steps as upgrading, just in the opposite direction. ;)

Navigate to Seal Subscriptions > Settings > App plans.
Here, choose a plan that is lower than your currently selected one. A pop-up window will appear, asking if you really want to downgrade. Click “Yes, downgrade ” and you'll be redirected to the Shopify's "Approve subscription" page, where you will replace the current subscribed plan with the one you selected.

You could also downgrade all the way back to the FREE plan.