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.
Get a refund - Apple (iOS)
Before asking for a refund, you should cancel your active subscription, otherwise it's very unlikely that Apple will grant you a refund. Learn how to do it here.
If you purchased a Speech Blubs or Lingo Blubs subscription via iTunes in the 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. To get your money back please follow the link ("Report a problem") that you received in your inbox from Apple (Receipt).