Hi Trakarn,
Hope this email finds you well. Thanks for taking the time to contact us. My name is Thyrose, your iTunes Store Advisor.
I understand that you were charged twice for a recent in-app purchase you made. I know the importance of making sure your money is accounted for and spent wisely. Rest assured that I’ll look into this and investigate the possibility of providing a refund.
I’ve reviewed your case and issued a full refund for the duplicate purchase. Within ten business days, 2.99 USD should be posted to the payment method used to make the purchase.
If your duplicate purchase was the result of receiving an error when downloading the first purchase, note that it’s best not to repurchase the item. Usually it’s still waiting to download in your account.
If you discover that iTunes is no longer showing a warning message for buying an item you already bought, you can reset your warnings. To learn how, see this article:
https://support.apple.com/HT201620
I trust that I was able to address your concern. Should you have any other questions, don’t hesitate to email back. I’ll be glad to help.