Cancel an app

Request a refund for an App Store or  iTunes Store purchase - Apple Support

Just so you know for future reference, you can’t cancel an App. When you tapped on Buy, you agreed to purchase it under Apple’s Terms of Sale which for the most part, don’t allow for refunds unless the app doesn’t work or doesn’t work as advertised. In other words, all sales are final.

You can request a refund, but Apple is under no obligation to grant your request.