There are many, many reports on the web about identical calls from this so-called collection agency.
This is a common scam, and if you know that you didn't take out any online loan, you're almost certainly right about it. In tough economic times, unscrupulous people buy up old consumer lists and old debts and then reach out to people and try to intimidate them into paying monies they don't really have to pay.
You have the right to ask this collection agency to send you written validation of any debt, because you are allowed this under the Fair Debt Collection Practices Act, a Federal act designed to protect consumers from predatory collection agencies. Once they send you written validation, you can formally dispute the debt, which you should do in writing, by sending the collection agency a cease and desist letter, letting them know that they are in violation of both state law and the Federal government's Fair Debt Collection Practices Act. Tell them in your letter to immediately refrain from contacting you again or anyone else such as your family or employer or that you will report them on the state level to your state Attorney General and on the Federal level to the Federal Trade Commission. Remind them that from here, every violation could get them fined $1,000.
If you really owe this money, they will have to serve you and sue you civil court, but they cannot continue to call and harass you. But if you don't owe the money, this should be the end of it all.
The Federal Trade Commission gives a wonderful overview of overaggressive and/or fake collection agencies and how to get them off of your back, where to report them, where to learn more, etc. And it is pretty straightforward. You can access that here.
If these are out and out scammers, they may not respond to threats of Federal law, but you can simply ignore them and report them to our police, to your state attorney General, to the FBI at IC3.gov and to the Federal Trade Commission at FTC.gov Good luck!