It's technically impossible for us to refund payments made via the App Store.
Please, contact Apple Support directly: https://support.apple.com/
Tips to avoid Accidental Purchases:
https://support.apple.com/en-us/HT204396
Tips to avoid Underage Purchases:
- Ask to Buy
- Screen Time Settings
Please check that you have Purchase Restrictions set up on your devices (Settings -> General -> Restrictions) to avoid unauthorized payments.