The national fraud and cyber crime chief of the City of London Police, Jonathan Frost, called up Calcutta police commissioner Anuj Sharma on Friday to congratulate him for busting a fake call centre racket that had duped almost 23,000 people in the UK.

The call came at the Calcutta top cop’s mobile number around 2pm, or around 9.30am in London.

Earlier this month, Calcutta police had closed down two fledgling call centres in the heart of the city, whose employees were allegedly posing as members of the Microsoft technical support team and swindling customers in the UK and the US out of lakhs of rupees. In many cases the racketeers had got hold of the customers’ bank details, causing huge monetary losses to them.

During two simultaneous raids, the detective department of the Calcutta police had arrested seven people connected with the two call centres — one located in Topsia and the other on Rafi Ahmed Kidwai Road.

Frost, the director of the National Fraud and Cyber Crime, City of London Police, thanked Sharma for the intervention of the Calcutta police in cracking the case.

“We have assured them of help in future if there is any specific input,” Sharma told Metro after talking to the cyber crime police chief of London.

The call centres were targeting UK and US citizens, calling them to say their computers had been affected by a virus and the devices needed immediate debugging. Scared, the customers would either pay for a fake anti-virus programme or provide vital details about their computer system that would give the fraudsters access to the financial data stored in them, an officer said.

The London police had conveyed to Lalbazar that the racket had duped around 23,000 people in the UK.

The detective department had swung into action and zeroed in on the call centres following two complaints from Microsoft.

Sources in Lalbazar said the City of London Police had been trailing the fraudsters over the past few months. The London police and Microsoft jointly raised an alert when complaints started pouring in about how people in the UK were getting calls from “Microsoft” and were being left poorer by thousands of dollars.

In one of the awareness tweets shared by the City of London Police, they warned: “Hang up the phone if someone calls you out of the blues and says there is something wrong with your computer.”

A senior officer in Lalbazar said being thanked by the City of London Police was in itself a matter of pride for Calcutta police whose seeds were sown in the British era.

Calcutta police was part of the British colonial administration in the pre-Independence era. Post-Independence, it was reorganised under the leadership of the first Indian Calcutta police commissioner Surendra Nath Chatterjee.

Sharma was the 40th and is now the 42nd Calcutta police commissioner. He was removed briefly before the Lok Sabha elections.