Accidental purchase
requesting contact information to help with a refund from accidental app purchase
Get help with an item purchased from the App Store, iTunes Store, or iBooks Store - https://support.apple.com/HT204084
Report a Problem to request a refund - http://reportaproblem.apple.com - "Sign In for help with iTunes purchases made in the last 90 days"
If a reporting a problem request is unsuccessful you can also try:
Other ways to contact iTunes Support:
https://www.apple.com/emea/support/itunes/contact.html
https://support.apple.com/country-selector/itunes
Apple's terms of purchase for most countries are effectively, "All Transactions are final" (check terms at: http://www.apple.com/legal/internet-services/itunes/). Apple may refund on a case by case basis, but realize they can also say no.