The iTunes App store sales policy clearly says that you cannot cancel a purchase or receive a refund for a purchase but they are known to make exceptions if you have a valid reason.
Here is a clear example of how to ask for the refund to Apple http://www.labnol.org/software/itunes-app-store-refunds/13838/
Anyway if you are facing an issue you can ask a refund, the apple rules don't allow us to refund the customer because they can do it directly.
Instructions how to do:
Please feel free to contact us for any more information.