The scammers operate under names such as U.S. National Bank, Federal Investigation Bureau and United Legal Processing, said West Virginia Assistant Attorney General Norman Googel.
The callers also have invoked the names of actors Denzel Washington and Steve Martin, people who've received calls tell ABCNews.com.
Googel said that the scammers have been impossible to track down, but ABCNews.com spoke to one man who claimed to be associated with U.S. National Bank. The man said he works for Financial Crime Division, a company he said provides services for USNB.
The man refused to give his name and gave little information about his company.
"It's not necessary that each and everyone knows about Financial Crime Division, and probably one of them is you," he said. (To hear an excerpt of this interview, click here. Links to more interview excerpts are included on the second and third pages of this story.)
The man also denied that consumers had been threatened with arrests.
But Mark Feury, a 35-year-old assistant manager at a hotel cafe, said it was the threat of an arrest that drove him to wire nearly $800 to U.S. National Bank in January. The Lewisberg, W.Va., resident said that he took out several payday loans -- short-term loans -- in 2005 to help pay for Christmas presents and medical treatments for his son, who suffers from autism.
Feury said he paid his loans back in 2007, but the scammers' phone calls -- at least 35 in all, he said -- and their threats made him doubt himself.
"I was scared to death," he said. "Everything they said literally just stressed me out to the max."
The group has targeted consumers who took out payday loans through Web sites years ago, Googel said.
The group has secured consumers' Social Security numbers and other personal information, which may have been stolen from Internet payday lending sites, Googel said.
What has made the group especially intimidating, Googel said, is its use of phrases that sound like legal terms -- such as "downloading affidavits" -- but, in reality, are meaningless.
The alleged scammers have also invoked God, Googel said, telling victims that "only God can help you now."
Some of the scammers' tactics are downright puzzling.
One West Virginia woman, who asked that her name not be revealed, told ABCNews.com that a scammer once called her and identified himself as "Denzel Washington."
Feury said that one of the scammers who called him said he was calling from "Steve Martin's office."
Googel said that the scammers' use of celebrity names may indicate a lack of familiarity with American names. Some, he said, suspect that the scammers are based in India.
Since July 2007, Googel said, the West Virginia Attorney General's Office has heard from nearly 20 consumers who have complained about the scam.
West Virginia residents aren't the only ones complaining. The Florida Attorney General's Office said it has heard more than three dozen complaints related to U.S. National Bank.
Thus far, Googel said, the scammers have been impossible to trace, using a multitude of phone numbers and fake addresses.
"The way they've hidden themselves is pretty slick," he said.
ABCNews.com called a phone number associated with U.S. National Bank -- Feury listed the number in a complaint against the company -- and was transferred to the man who claimed to work for Financial Crime Division.
The man, who spoke to an ABC News reporter for about five minutes, said that U.S. National Bank owns Internet payday lending Web sites and that Financial Crime Division is a "legal affidavit processor" -- a term that Googel also has dismissed as meaningless -- that works to notify borrowers that they still owe money to USNB. (The man refused to provide ABC News with contact information for U.S. National Bank.)
"They have taken so many loans they have forgotten that one to pay back and we are calling them about this legal matter," the man on the phone said. "That's not our problem that they have forgotten."
The man argued against the complaint that his company had called people about nonexistent or repaid debts. Consumers, he said, have failed to provide the company with proof that their debts have been repaid.
"When we are asking the information, they are not ready to give to us," he said. "If they have paid it, they must have something in writing, some kind of receipt, but they are not going to give it to us, so how can we trust them?"
When asked where Financial Crime Division was based, the man hung up.
Googel said that he has been on the phone with the suspected scammers many times and that each time they refuse to provide identifying information such as valid addresses or a licensing number, which collections agencies operating in West Virginia are required to have.
"I yell and scream at them, but it doesn't do any good. It's sort of high drama in a way," he said.
Googel said that he has notified the Federal Trade Commission about the scam, but the FTC would not confirm whether it had launched an investigation. An FTC official told ABCNews.com that it does not disclose whether it is investigating a company unless it takes the company to court.
The official said that consumers with complaints about U.S. National Bank are encouraged to contact the FTC, the Better Business Bureau or their state attorney general's office.