I want a refund on an app i just purchased

What do you mean 'cost me a sale on ebay' ? Refunds are generally only given for apps that don't work as described on the description page in the store. If the app isn't working on your iOS device, and you've tried deleting and redownloading it via the Purchased tab in the App Store app on the device, and you've tried contacting the developer, then try the 'report a problem' link to contact iTunes Support : http://reportaproblem.apple.com

If the 'report a problem' link doesn't work then you can try contacting iTunes Support via this page : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption