While we’ll be sad to see you go, we still make it easy for you to cancel. Just go into your account and click ᴇᴅɪᴛ under Your Subscription(s), then click the ᴄᴀɴᴄᴇʟ sᴜʙsᴄʀɪᴘᴛɪᴏɴ button at the bottom of the page. Easy peasy.
Please note that canceling your subscription only stops the subscription going forward (meaning there won't be any future renewals). It will not, however, affect any boxes that have already been paid for; those will still be good to go!