An In-App Purchase did not go through, yet I was still charged - how would I get reimbersed?

I purchased 900 donuts in The Simpons Tapped out, and it charged me, yet none of them showed up in game, and subsiquently did not allow me to load the game. I had to restore my iPod and the game came back with again, no donuts and still a charge of $50 on my credit card, how and who would I contact to get reimbersed? This apple website is a bit confusing for me to understand since I am unfamilar with it and would like to get a refund ASAP,

Thanks in advance for any help!