Unauthorized payment and refund

My friend’s kid had my ipad and accidentally bought in-app items. I contacted Apple in website and phonecall right after I found this.( about one day after the purchase when I got notice by my Iphone bill message. )

And now Apple costermer survice keep saying that I didn’t meet the standard of refund and didn’t give me precise reasons why. She even told me to contact the app’s company by myself, which the company has noted that the only way to ask for refund is to go to Apple.

and so, I am calling for help. The payment system really didn’t annouce me of any paying proceeding notice so I couldn’t stop this in the first place. Though I have contact Apple in the very beginning, the costermer service refuse to help.

So who and where can I contact next? And how could I deal with this ?

Thanks.