A business in Kailashahar is a long bus ride from most of its buyers. The tea packer's shops are in Agartala, the travel desk's guests are on a train somewhere south of Kumarghat, and the bus counter's passengers are bound for Silchar or Guwahati. Very little is settled face to face, which is why so much of it already happens on WhatsApp.
What changes on the API is not the conversation but who can hold it: two people on one number, a confirmation that goes out the evening before without someone typing it, and a clear line between a message about a booking and a message about next season.