What should I do about an in-app purchase that has been charged to my account but didn't download?

Hello,

So last night I downloaded another installment of a storyline from Pirates in Love application. Normally what occurs is a downloading of material and than I'm allowed to play the game, however this time around nothing happened at all. So I figured that this only meant that it didn't process my order and I would deal with it in the morning. However, this morning I looked on my account information and noted that it had in fact charged me for the purchase that I did not receieve from the makers, does anyone know what I should do to either get the money back, or get the installment to appear on my iphone? It would be much apperciated.