Sending a WhatsApp template message will incur charges from Meta. Meta's charge is associated with the category of the template (marketing, authentication, or utility). This excludes utility template messages sent within a customer service window; if you send a utility template message within a customer service window, Meta' fee will be waived. Meta charges Marketing and authentication template messages even if they are sent within a customer service window.
Additionally, Meta will waive their fee for non-templated messages sent within a customer service window. Note that non-templated messages can only be sent within a customer service window.
Learn more about how you can use the Sinch WhatsApp Business API to send messages easily and securely.