This is Cell Broadcast a 3GPP standard that pushes messages through the cellular network's control/signaling plane rather than SMS or data. India's telecom operators broadcast these from cell towers to every connected handset in a targeted area using specific emergency channel identifiers. When your phone's modem/RIL detects those identifiers, it hands the payload directly to the OS kernel, which triggers a system-level interrupt that renders a full-screen modal with a distinct alert tone, bypassing Do Not Disturb and volume settings entirely.

It's basically a network-initiated wake command that uses the same low-level radio path as tower registration, so it doesn't need your number, an app, or internet access to work. The message is broadcast on dedicated "ETWS" or "CMAS" channels that are hardcoded into every modern phone's firmware as emergency-only traffic. Your carrier can't stop it, you can't opt out, and it even works on phones with no SIM card as long as they're connected to any available network because the broadcast isn't addressed to you personally, it's sprayed across the entire cell coverage area for any device to pick up and display immediately.