If you've made it to the Profile page in your App Store app or the Apple ID page in your Settings app, and still can't find the "Manage Subscriptions" button, it means you currently have no active subscriptions to cancel. All you have to do in this case to say goodbye is delete our app and be on your way. We're sad to see you go, but we wish you all the luck and joy in the future.
If you're not convinced, let us know at firstname.lastname@example.org. We'd be happy to investigate matters further.