As in-game purchases are controlled by 3rd party platforms (in this instance, Facebook), for us to be able to see them and take action on them, we need for you to first ‘dispute’ the purchase via Facebook.
To do this, go to your Facebook news feed on a PC/Laptop and click the down arrow by your avatar at the top right of the page.
Then select Settings & Privacy > Settings.
Next, please select Orders & Payments/ Facebook Pay from the left-hand side of the Account Settings page.
You'll then be shown all the transaction history of purchases you've made on Facebook. Just click the one for the relevant game, and you'll be able to 'dispute' it. For more information, please visit Facebook's Help Center