What is DND in calling, and how DLT and 1909 fit in

General information, not legal advice. Checked against official TRAI and PIB documents on 6 October 2026.

DND, short for Do Not Disturb, is the preference an Indian mobile user registers with their operator to control commercial calls and messages. It is set by calling or texting 1909, by USSD code, through the TRAI DND app or through the operator, and it can block everything or only chosen categories, such as banking, real estate or education. The preferences sit in the National Customer Preference Register, or NCPR. DLT is the machinery behind it: TRAI’s 2018 regulations make operators run commercial communication through distributed ledgers that record who the registered senders are, which headers and templates they use, what consent they hold, and what each customer has blocked. Since the 2025 amendment, promotional calls must come from registered senders on 140-series numbers, and the 1600 series carries service and transactional calls. Ordinary 10-digit mobile numbers may not be used for telemarketing. A calling CRM app like Weo Dialer runs on those ordinary SIMs, so the people it calls should be people who asked.

DND in calling terms

DND categories and 1909 codes

TRAI’s schedule lists the options a person can choose by USSD:

• Full block: 19090#
• Promotional block: 190950#
• 1 Banking, insurance, financial products and credit cards
• 2 Real estate
• 3 Education
• 4 Health
• 5 Consumer goods and automobiles
• 6 Communication, broadcasting, entertainment and IT
• 7 Tourism and leisure
• 8 Food and beverages

Each sector code is dialled the same way, for example 19092# for real estate. TRAI’s 2026 press release adds that a person who has blocked a sector will not receive 140-series calls from entities in that sector.

DLT in calling and messaging

DLT is the part most businesses meet first, usually when they try to send bulk SMS. Under TRAI’s 2018 regulations, operators must use permissioned, private distributed ledgers so that regulatory checks happen before a commercial message or call goes out. A sender registers with an operator, registers its headers, and registers content templates for promotional and service communication. Since 2025, business SMS headers carry a suffix that shows the type: -P for promotional, -S for service, -T for transactional and -G for government.

For voice calls the “header” is the calling number itself, taken from the special series: 140 for promotion and 1600 for service and transactions.

DND in calling and the 140 and 1600 series

The 2025 amendment closed the gap that let telemarketers call from ordinary numbers. PIB’s summary says senders may not use normal 10-digit numbers for telemarketing, that the 140 series continues for promotional calls, and that the new 1600 series is for transactional and service calls. TRAI’s 2026 press release mandates 140xx for promotional calls by entities of any sector, and 1600xx for service and transaction calls by banks, insurers and other entities regulated by RBI, SEBI, IRDAI or PFRDA, and by government bodies.

Breaking these rules has real costs. Since the 2025 amendment a complaint can be made within 7 days, and a first proven violation bars outgoing services on all the sender’s numbers for 15 days, with one-year disconnection and blacklisting for repeat violations. The full sequence, including what counts against unregistered senders, is on the auto dialing rules in India page.

DND in calling example

An illustration with made-up names, not a customer result.

A furniture store in Visakhapatnam keeps a list of past buyers and new enquiries. One customer, Ms Lakshmi, has blocked category 5, consumer goods, through 1909. If the store hired a registered telemarketer to promote a sale from a 140 number, that call would not reach her.

A different situation: she bought a sofa last month and the store’s delivery team calls from a staff phone to fix a delivery slot. That call is about her own order and carries no promotion, which is the kind of service call the rules treat separately. If the caller adds “and we have a sale on dining tables”, the call has become promotional. The store’s sales team keeps her marked as an excluded number in its calling CRM after she says she does not want offers, so she is left out of every calling session from then on.

DND in calling limits

What DND does not do:

• It does not block personal calls or calls from people you know.
• It does not stop fraud on its own. Suspected fraud calls are reported on Sanchar Saathi’s Chakshu, and unsolicited commercial calls through 1909.
• It does not give an ordinary SIM permission to call DND-free numbers. A number not registered for DND is still not a licence for telemarketing from a 10-digit mobile.
• It does not replace your own records. Keeping proof of each enquiry and honouring “stop calling” requests is the sender’s job; how lead sources help is explained under lead source meaning.

DND and DLT in calling FAQ