I've now been billed for two months of Shopify that I didn't want. You guys make it impossible to find the cancel button. Every single post says, go to "Shopify Admin" (There are no web pages with that name in the title). Go to "Settings" > "Plan" (There is no "settings" page. There is no "plan" page).
This is notification that you need to cancel my account. This is documentation for when I start attempting chargebacks on every shopify transaction on my account. Do something.
Edit: Obviously I found it as soon as I posted this message. It wasn't anywhere they said it would be, of course. I can't go back to the page because the store is deactivated but if I recall it was under "Billing" > "View All Bills", only then was there a three dot button next to my plan, with "Manage" or something or other, then finally from there I could deactivate. Truly a masterwork of hostile UI designed to annoy you into letting them suck you dry. Hats off to all the UI designers dutily engaged in this waste of everyone's time.