To cancel a recurring payment charge, you'll need to sign in to your iStall account settings. This can be done by clicking Sign In on the top right hand corner of the page, and then selecting "Account Settings". If you are having trouble signing in, see here for more details on resetting your password.
Skip this step if you clicked directly on the (account) link above. Once you are logged in, select Account on the top right, and then click on Settings.
In Settings, click on Manage Recurring Payments, or simply click the button below.
You will then see a listing of your current recurring monthly payments. To cancel recurring billing for your iStall parking stall, simply click Cancel under the Action column on the right.
That's it! You're done. At midnight at the end of the current month, this parking stall will become available for someone else to rent, and you won't be charged for its use.
(Here's that button again in case you want to do this now.)