Meta's pricing as of 2024-2026 (India rates): authentication ~₹0.10/conversation, utility ~₹0.30, marketing ~₹0.85, service free if reply is within the 24-hour customer-service window.
A 'conversation' opens when you send a template (or a customer initiates contact) and lasts 24 hours. Within that window, unlimited messages exchanged with that customer are included. After 24 hours, the next message starts a new conversation with a new charge.
Free tier: 1,000 service conversations per month per number — used to be marketing+utility; now restricted to service only.