Purchases made through the app are processed via iTunes, Google Play, depending on your login options and device.
The available payment methods vary by country some additional options may be:
Store credit, including iTunes Store Gift Cards, Gift Certificates, and Allowances
PayPal (requires the account to be linked to a credit card)
Mobile phone billing (through supported carriers)
Encountering a purchasing issue while playing on the mobile app? Make sure to fully close the app and reopen it before trying again!