In order to use Sinch Instagram service, the business must contract Sinch Conversation API which will allow you to provision the Sinch Instagram service. As Facebook does not charge anything for the use of Instagram service, Sinch also does not charge extra for the use of Instagram service, however, the business must pay for any fees associated with the Sinch Conversation API.
Please contact your Sinch Account Manager or you can contact Sinch directly for more details of the pricing.
Learn more about the Sinch Messenger API for Instagram.
