I didn't authorize this purchase

Hello. I would like to ask for a refund for the purchased app in the App Store. The reason is that a child was playing on the phone and downloaded the app without my knowledge. I later uninstalled the app without knowing that there is an automatic paid subscription for one year. Through 3 days free trial of an app had finished and on 6th May 2019 at 02:58 ET I got a notification about app purchase for 2 390 rubles. I would really appreciate your help with this.