You need to cancel the subscription—>View, change, or cancel your subscriptions - Apple Support. Deleting the app does not cancel the subscription. The app cost and subscription cost are clearly described in the app’s description in the App Store, so the charge should not have been a surprise.
After canceling you can request a refund, but Apple is not obligated to grant one. They frequently will if it was a recent charge and you haven’t gotten other refunds, however.
Use this link to request a refund—>Request a refund for apps or content that you bought from Apple - Apple Support
That link is automated and may refuse the refund. If it does contact Apple’s iTunes Store team and talk to a real human being:
iTunes Store - Contact Us - Official Apple Support