DND was introduced in 2007 and tightened progressively. Under the 2018 Telecom Commercial Communication Customer Preference Regulations (TCCCPR), unsolicited commercial communication via SMS or voice call is restricted unless the recipient has registered DND off, OR the sender has explicit opt-in consent.
For Indian SMBs sending SMS or making outbound calls, DND compliance is enforced via the Distributed Ledger Technology (DLT) platform. Every promotional SMS must be sent through a DLT-registered template via a registered Telemarketer. Bulk-SMS gateways (MSG91, Gupshup, Kaleyra) handle the DLT registration on your behalf.
WhatsApp messaging is not directly under DND — Meta has its own opt-in/quality rating system. But voice calls (including AI voice agents) DO fall under DND, and bulk-call campaigns to DND-registered numbers attract penalty.