Go to /help/cancel-subscription and enter the e-mail you subscribed with. If there's a subscription on that address, we e-mail it a one-click cancel link.
The link works once, for 72 hours. It opens a page that shows your subscription; pressing Cancel my subscription cancels it. Opening the link changes nothing by itself.
For your privacy the page never says whether an address has a subscription. No e-mail after a few minutes? Check spam, or send a change request ("Cancel my subscription") and a person will cancel it for you.
Something not right with a charge?
Send a change request: billing mistakes our records prove are refunded automatically, and a person answers the rest within two business days.