If you're referring to purchases made with your credit card which you want a refund for, you can tap here. This is the correct article if you're referring to purchases you've made in-game using the Gems or Coins.
Every time you purchase or use any currencies to upgrade an Item, you'll be prompted to tap the value again to ensure that you validate it before spending your currencies.
We understand that, even with this, sometimes accidents happen. In cases like this, we really would like to help you, but if we return the currencies and remove the item from your account, the game will suffer from adverse effects, and your gameplay will be negatively affected.
That's why we are unable to revert an in-game purchase.
If you believe you were overcharged (while factoring in the additional taxes and charges added by Google/Apple) or the item you've purchased still needs to be delivered, we're here to help! Tap here to check how to contact us!