They see WhatsApp.
You see JSON.

A real number on their side. A webhook and one REST call on yours.

{ "from": "15550123456",
  "text": "Hi! Did my order ship yet?" }

{ "chat": "15550123456",
  "text": "Yes! It left this morning…" }

• Free 3-day trial, $0 until it ends
• $5 per number per month, unlimited messages
• No Meta approval, no templates, no infrastructure