If you purchased a Calm subscription via iTunes in the Calm app on an iPhone or iPad and would like a refund, you must contact Apple directly, as they do not provide us with the ability to process refunds. Only Apple can process refunds for purchases made through an iTunes account.
You can contact Apple Customer Support directly at https://getsupport.apple.com/. When you get to this page, click "Billing & Subscriptions" followed by "Subscriptions & Purchases." Once here, you'll be given a variety of avenues through which you can contact Apple.