Any purchases you make in War Planet Online are handled via Google Play or the App Store and, as such, Gameloft assumes no responsibility for the process. Kindly note that prices may vary by the platform you are playing on, the country you are playing in, and some other factors.

Android:

You can find the receipts in your Purchase History on Google Play. Just go to Google Play’s support pages here, or you can visit Google Payments Center directly here.

iOS:
If you want to review the list of games, apps, subscriptions, music and other content you've bought recently, you can find your purchase history online here.

Note that the links will redirect you out of the game.