A sudden “No Service” message on a mobile phone may be an early warning sign of SIM swap fraud, a cybercrime in which criminals activate a duplicate SIM linked to a victim’s mobile number and use it to intercept banking OTPs, alerts and authentication messages. Cybersecurity experts say the fraud can allow criminals to access bank accounts and digital payment platforms within minutes.
Duplicate SIM Used to Capture OTPs
In SIM swap fraud, criminals first gather personal information through data leaks, fake KYC calls, phishing campaigns or social engineering. They then use these details to deceive telecom service providers into issuing a duplicate SIM card in the victim’s name.
Once the duplicate SIM is activated, the original SIM stops working and the victim’s phone may suddenly lose network connectivity. Banking OTPs, password reset messages and authentication codes then begin reaching the fraudster instead of the account holder.
Complaints and Losses Rise
According to industry estimates and cybersecurity data, more than 90,000 complaints related to SIM fraud were reported across India in 2024, with estimated financial losses exceeding ₹500 crore. Experts said salaried employees, business owners, senior citizens and ordinary banking customers can all become targets, especially when their bank accounts are linked to mobile numbers.
Cybercrime expert and former IPS officer Prof. Triveni Singh said SIM swap fraud is driven largely by social engineering. He warned users to treat an unexplained “No Service” message as a possible cyberattack and immediately contact both their telecom operator and bank, as fraudsters may exploit the stolen number within minutes.
Immediate Action Advised
Prof. Singh said India’s reliance on SMS-based OTP authentication creates opportunities for cybercriminals. He recommended additional identity verification by banks when a SIM has been recently replaced, stronger monitoring of high-value transactions and temporary blocking of suspicious activity until proper verification is completed.
The Government of India has also intensified action against telecom-enabled cybercrime. According to the Ministry of Home Affairs, large numbers of fraudulent SIM cards and suspicious IMEI numbers have been blocked, while systems have been introduced to identify spoofed international calls used in financial scams.
Experts advised users to treat sudden loss of mobile network as a financial emergency. They said victims should immediately contact their telecom operator and bank, temporarily block internet banking and UPI services, report the matter through the National Cyber Crime Helpline 1930 or the National Cyber Crime Reporting Portal, and enable safeguards such as Aadhaar biometric lock, SIM PIN and banking alerts.
