in itunes store select "account". then select "purchase history", scroll to the bottom and press "report a problem". find the item purchased that does not play properly and once more select "report a problem" once you have done this you are taken to another page where you are finally able to report the problem. When explaining the problem you have to be specific or they will not reply or do anything. It takes a couple of days but they will refund your money and in my case gave me a couple of free downloads due to my long and extensive purchase history.