Purchases in the in-game shop are processed by either Google Play or iTunes, depending on the device you're using.
Payment methods available may vary by country and/or your phone provider, but you can usually use the following methods:
- Credit or debit cards
- Direct carrier billing
- iTunes cards
- Prepaid or gift cards
- Store credit (including Allowance Account balances)
For further information on payment methods available to you, please contact the iTunes or Google Play Customer Support services.