If you or a family member completed an accidental purchase, you can request Apple or Google to process a refund. Please contact them with the according links below:
We also recommend that you use restrictions on your device to avoid accidental purchases. Specially if a child has access to your device.
Open "Google Play" App, go to Settings, scroll down to 'User Controls' and tap the desired option on 'Required authentication for purchases'.
On your iphone, ipad, or ipod touch: Go to Settings > General > Restrictions
You can follow this simple guide: https://support.apple.com/en-gb/HT204396