Business messaging is how a company sends you an SMS, a WhatsApp message or a phone call from its own software, with no person typing or dialling. The platforms that do this are called communications platform as a service, or CPaaS. Think of three things that reached your phone this week: the one-time password (OTP) from your bank, the WhatsApp message saying that your order has shipped, and the call from the delivery rider who could not find your gate.
Messages that a business sends to a person are called A2P (application-to-person) messages. Mobile operators such as Jio, Airtel and Vi check and price them separately from the messages that people send each other. In India, every business must also register its sender name and the wording of its messages with the operators, under rules set by TRAI, the telecom regulator.
Here is a typical case. You open a shopping app in Guwahati and order a pair of running shoes for ₹2,499.
First, you sign in. The app asks for your mobile number. Its OTP verification service creates a six-digit code and sends it to you. Some apps first ask your operator, through network APIs, whether your SIM card was replaced in the last few days. A recently replaced SIM is a common sign of fraud.
Second, the app's code sends the message. A developer at the shopping company wrote a few lines of code that call a messaging and voice API platform. An API is a fixed format in which one program asks another program to do something, here "send this text to this number". Larger apps first pass each message to a notification service, which decides whether it goes by app notification, SMS or WhatsApp.
Third, the SMS reaches your operator. In India, it usually passes through an A2P SMS aggregator, a company with direct connections to every Indian operator. At the operator, an SMS firewall checks the message and blocks messages from unregistered senders. Your OTP passes, and it arrives within a few seconds.
Fourth, two days later, the shipping update arrives on WhatsApp. It comes through the WhatsApp Business API, which lets a business send messages, catalogues and payment requests inside WhatsApp. You reply in the same chat to choose a delivery time.
Fifth, the rider calls. Your phone shows a number that is neither yours nor the rider's. Number masking connected the call through a temporary number, so neither of you sees the other's real number.
You never deal with the CPaaS companies yourself. The shopping company pays them for each message and each minute of calling. More and more of these chats and calls are now handled by AI customer service agents instead of fixed menus.