To set up a payment method for your WhatsApp Business API Account, follow these steps:
1. Go to the payment center of Meta from the Meta Business Manager:
https://business.facebook.com/billing_hub
2. Select your Meta Business Manager.
3. Click on “Payment Methods”.
4. Select “WhatsApp Business Account”
Then, select your WhatsApp Business Account from the dropdown menu and click on “Add a payment method”
Finally, enter your payment information.