You can easily downgrade your Submittable plan to an Inactive plan.
- Click on More in the upper right corner of the screen. Select Account.
- Select Subscription Plan on the left
- Click the Change your plan button in the center of the page.
- Select your new plan.
You will be prompted if you need to make any changes (for example remove team members) before your plan can be changed.
You can keep your account set up in Submittable with the Inactive plan and make all of your categories not Live (which will effectively turn off your public-facing site), in case you want to return to use it in the future. Or email email@example.com to remove it altogether.