Inbox (top navigation) is one conversation thread per client, whatever channel they use.
- Clients can reply to your emails, text your business number, message on WhatsApp, or write from their portal. It all lands in the same thread.
- Replies go back on the channel they used (a WhatsApp conversation stays on WhatsApp; texts by SMS; otherwise email), and the thread shows how each message was actually delivered.
- Quotes sent, invoices sent and reminders are logged into the thread automatically, so the whole relationship reads in one place.
SMS and WhatsApp share a monthly text allowance, see the SMS pack under Settings.