Accidentaly brought Core Tunnel, but wanted Core Shell

[yang (Yang.Y)]

The apps selling on App Store are controlled by Apple, developers have no permission to revoke a purchase. So I can't help you with that, you must contact Apple for support, please check this post to get a refund from Apple:

Get a refund for Premium features

If you’d like a refund for Premium features in Core Shell / Core Tunnel, you must request a refund from Apple. You won’t be able to use Premium features from the App Store after your purchase has been refunded. Visit https://reportaproblem.apple.com/ Sign in with your Apple ID. Click “Report a Problem” on the relevant Purchase. If you have any trouble, post a topic or send @yang a personal message.