By mistake I purchased the wrong item
How can I get the. Right coins for my game
Purchases are considered final but you can try the 'report a problem' link to contact iTunes Support and see if they will refund or credit you so that you can buy the correct item : 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