Miteshkumar Patel, 42, who is based in Illinois, pleaded guilty to money-laundering conspiracy, joining six others who have entered similar pleas.
The 24 men, along with 32 others who are in India, are accused of defrauding US residents of hundreds of millions of dollars.
As iTWire reported last year, the call centres named in the indictment are HGlobal, Call Mantra (aka Robust Inc, Raytheon International), Worldwide Solution, Zoriion Communications and Sharma BPO Services, all of which are located in Ahmedabad in the Indian state of Gujarat.
In other cases, they impersonated officers from the US Citizenship and Immigration Services and misled US residents into believing they would be deported unless they paid fines for alleged irregularities with their residence papers.
US residents were also misled into believing that they were eligible for so-called payday loans and that they needed to pay a small fee upfront to indicate that they had enough funds to repay the loan.
And in a fourth set of cases, the call centres misled Americans into believing they were eligible for fictitious government grants and asked them to pay an upfront fee towards an IRS tax or a processing fee.
The scams began in 2013, according to admissions made by Miteshkumar who is to be sentenced on 7 March next year.
The other 17 US-based defendants are: Bharatkumar Patel, Ashvinbhai Chaudhari, Harsh Patel, Nilam Parikh, Hardik Patel, Rajubhai Patel, Viraj Patel, Dilipkumar A. Patel, Fahad Ali, Bhavesh Patel, Asmitaben Patel, Montu Barot, Nilesh Pandya, Dipakkumar Patel, Nisarg Patel, Rajesh Kumar, and Dilipkumar Ramanlal Patel who previously pleaded guilty on various dates between April and September 2017.
The break-up of people charged and their affiliations – HGlobal: 18 each in India and the US; Call Mantra: three each in India and the US; Worldwide Solution: two in India, three in the US; Zoriion Communications: seven in India; and Sharma BPO Services: two in India. This makes for a total of 32 people in India and 24 in the US.