SIM activation and retail apps are the software that sets up a new mobile customer, and the apps that shops and agents use to sell SIMs and recharges. Activation means checking the buyer's identity, linking the SIM card to a phone number and switching the SIM on. The same software manages the operator's stock of phone numbers. It also handles a number that moves to another operator, which is called porting.
In India, most SIMs are sold at small mobile shops, not at the operator's own stores. The shopkeeper is a registered agent of the operator, called a point-of-sale agent. Each agent uses the operator's retail app on a phone, with a small fingerprint reader attached to it.
Consider a construction worker from Odisha who buys a new SIM at a mobile shop in Madurai. The agent opens the retail app and scans his fingerprint against his Aadhaar. This step is e-KYC, the electronic form of KYC (know your customer). UIDAI, the body that runs Aadhaar, confirms the fingerprint and returns his name, address and photo. The app also takes a live photo of him, and compares it with the Aadhaar photo through an identity verification check. Then it checks that he does not already hold nine SIMs in his name, which is the limit in most states.
Next, he chooses a number from a list of 20 free numbers. The activation system links that number to the SIM's own identity number, which is stored in the SIM's chip. It records the link in the network's subscriber database. The packet core checks this database every time the phone connects. The system also creates his account in telecom billing and real-time charging. He pays ₹199 for his first recharge, and the agent earns a small commission on it. About half an hour later, the SIM connects to the network.
The rules are stricter when an existing customer asks for a replacement SIM for the same number. After the replacement, SMS messages are blocked for 24 hours. This is because criminals sometimes get a replacement SIM in someone else's name to receive that person's OTPs. The 24-hour block gives the real owner time to notice and complain.
The same retail app is used for recharges. Shops keep a balance with the operator, and each recharge they sell is deducted from that balance. Activation can also set up extra services tied to the number, such as operator-branded cloud storage. Brands that sell plans on another operator's network, called MVNOs, use the same kind of activation software.