Business Chat will be available in Spring 2018.
Apple introduced Business Chat in iOS 11.3. It is currently in beta so functionality may change. Business Chat allows you to talk with a customer service representative through iMessage for any participating business.
You can identify a participating business by the Messages icon next to their name in Spotlight search, Siri, Safari or Maps. To start a chat thread, just tap the Messages icon and you will be taken to iMessage where you can then chat with a representative for that business.