WhatsApp Business ↔ WhatsApp Consumer. Same chat shape on both sides — the
asymmetry is just business mode vs consumer mode. Your
business contact (10-digit code) is what customers pay; incoming receipts
arrive in the thread as messages from the customer's masked number.
Polymorphic identity (D4): the same Pepper account can be both a customer and a business. Switch MSISDN to +2348012345001 and back to feel the two roles. Receipts are real-time (3s poll); Request Payment drops a short code in the thread that the customer types pay <code> against.