New Delhi, Jul 10 (PTI) No app can block phone calls originating from 1600 number series that are meant for communications by regulated entities and the government to citizens, telecom regulator Trai said in a statement on Friday.

The Telecom Regulatory Authority of India (Trai) has also clarified that promotional calls originating from 140 number series cannot be tagged or filtered by an app and can only be blocked by DND registry which is managed by the regulator. TRAI has also clarified that promotional calls originating from 140 number series cannot be tagged or filtered by an app and can only be blocked by the DND registry.

"Under the Telecom Commercial Communications Customer Preference Regulation (TCCCPR), any tagging, blocking or filtering of the calls originating from 1600 series numbers is not permitted," Trai said.

The regulator said that it has mandated the use of 1600 series numbers for service and transaction calls by regulated entities of banking, financial services and insurance entities regulated by RBI, SEBI, IRDAI and PFRDA to their existing customers and by government entities for government-to-citizen communication.

The key objective of assigning designated series for these important communications is to make such calls trustworthy for the citizens, the regulator said.

On calls starting with 140 number series, Trai said that it is meant for use by registered telemarketers.

"The customers have the right to allow or block promotional calls originating from 140 series numbers from entities of any or all sectors by registering their preference on the Do Not Disturb (DND) registry," Trai said.

The regulator said that a customer who has blocked any or all sectors from receiving promotional calls on the DND registry will not receive any calls from 140 series originating from entities of the blocked sectors.

"The customer can register his/her DND preference through multiple means including through TRAI DND App. Any tagging or filtering of calls from 140 series numbers is not allowed except for blocking on the DND registry, as any tagging can mislead a customer who has otherwise allowed receipt of such calls from a sector on the DND registry," Trai said.

The clarification from Trai implies that customers will not be able to tag calls from numbers starting with 1600 and the 140 number series as spam, fraud, or any other type of call.

Truecaller CEO Rishit Jhunjhunwala has said there has been a huge increase in spam calls through 140 and 1600 number series.

He said the number of spam calls made through the 140/1600 number series skyrocketed with over 5.1 crore calls from both series going unanswered every single day.

Specifically with the 1600 series, reserved for service/transaction related calls, we have seen daily blocking actions triple (up by 208 per cent) since October 2025. A total of 7.4 crore (74 million) manual blocking actions have been taken against these series in the past 8 months," Jhunjhunwala had said in a social media post.

He said that at present Truecaller users actively block 4 lakh calls from the 140 series and 1.25 lakh calls from the 1600 series every day. PTI PRS PRS MR

Caller identification rules for 140 and 1600 series calls limit app-based blocking, while DND registry controls promotional call preferences. Calls originating from the 1600 series are reserved for service and transaction communications by regulated entities and government entities, and tagging, blocking or filtering of such calls by apps is not permitted under the Telecom Commercial Communications Customer Preference Regulation. Calls beginning with the 140 series are meant for registered telemarketers, and customers may allow or block such promotional calls through the Do Not Disturb registry, including by using the TRAI DND App. App-based tagging or filtering of 140 series calls is not allowed.