There are two payment options available in the latest version of WhatsApp:
If you want to learn how a friend can pay for you, please read the How do I use Pay for a Friend? article.
You can pay in Google Wallet using carrier billing, a credit, debit or gift card, or PayPal. Once you start the payment process in Google Wallet, the available options will be displayed.
Google Wallet with carrier billing
Carrier billing is only supported for certain carriers. Please check this Google website to see whether your carrier is supported. If your carrier is supported, but you still cannot pay, please read the carrier billing troubleshooting section on that same page for the requirements you need to fulfill to use carrier billing.
Google Wallet with cards
If you want to pay for your WhatsApp subscription using a credit card/debit card/gift card but don't know how, read this information about changing your payment information...