Once the payment is complete and you see the “Purchase completed” page, the contents of your purchase will be automatically added to your in-game inventory. If the contents of your purchase are not immediately visible in your game, completely close the game, and then re-open it. Your inventory balance should now be correct. 

If you still did not receive your purchase, please contact player support. In the game, tap the "cogwheel" icon to open the settings menu -> tap "support" -> open an article, scroll to the bottom and tap the "chat with us" button.