Enable Click to Chat by WhatsApp button on your website.
This Sociocs plugin adds a chat bubble on your website that draw user's attention, and gives them an easy way to reach out to you. It converts an inquiry into WhatsApp based conversation, so that your user doesn't have to wait on the website for a response.
When your web app user initiates the inquiry, it shows up in your Sociocs Inbox, from where you can reply to the user, and continue the conversation.