Apple Store's Unresponsive Customer Service

I recently had a distressing experience with Apple Store. My young nephew made in-app purchases unknowingly, and despite the fact that my card had no limit, he managed to authorize not one, but two transactions! Days later, I encountered problems while attempting to download an app, only to discover that there had been unauthorized payments made to my account. I contacted customer service right away, hoping for a quick resolution. To my surprise, the representative simply stated that I owed money without providing an explanation. I insisted on not making these purchases, even though there was no credit limit issue. The response was to pay and request a refund, which I dutifully did. Despite my detailed explanation, Apple Store has yet to refund the nearly 400 TL they took from me for no valid reason. This has been a frustrating experience, and I urgently require a resolution.