Items bought through In-App Purchases (purchased with real money) are generally non-refundable. However, there are special cases where a refund can be granted, although the process for these transactions is handled by Google and/or Apple.
If you'd wish to request a refund for an accidental purchase, please check how to do it below:
Important: You can easily manage the ability to make in-app purchases, adjust password protection settings, or disable in-app purchases entirely through your mobile device’s general settings. Further information can be found herefor iOS and here for Android.