In this case please contact the Google Support:
https://support.google.com/googleplay/answer/2479637#apps&zippy=%2Capps-spiele-und-in-app-k%C3%A4ufe-einschlie%C3%9Flich-abos
As developers we are "only" the producers of the app, but it is sold via the Google Play Store. If you bought the product from Google, you have to contact the seller with your complaint.