not able to purchase hello kitty coffee candies

What happens when you try to buy them, does the 'buy' button not work, do you get any error messages ... ?

If you are getting a message to contact iTunes Support then you can do so via this link and ask them for help (we are fellow users on here, we won't know why the message is appearing) : 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

If it's a different problem ... ?

If you say what the problem is, then somebody on here might be able to help

You can use the link that I gave in first reply to contact iTunes Support and ask them for help - we are fellow users so we won't know why you are getting the message.