425-939-4889

I did.  Do you know who it is?

First of all, it is illegal for them to threaten to call your boss or to  share any information about the alleged debt with anyone but you. This is a common (and illegal) tactic that sleazy debt collector thugs use. (They also like to threaten people with arrest, etc. This is also illegal.)  

Since they've already broken the law, I'd immediately cease all communication with them and contact an attorney. If you don't have an attorney, I suggest you contact consumer law attorney Bud Hibbs ( http://www.budhibbs.com/First.htm ) or the National Association of Consumer Advocates ( http://www.naca.net/debt-collection-abuse ) for a referral.  I'd be that Bud or the NACA could refer you to someone who can assist in this matter. You may also want to check out http://www.fairdebtlawyers.com ; I think they work on contingency, too.

In the meantime, I'd send the debt collector a cease-communication notice via certified US Mail with a return receipt request. You can do this yourself or have an attorney do it for you. If you want to do it yourself, here are a few sample cease-communication letters that you can copy and adapt to your situation:

http://www.budhibbs.com/cease_comm.htm
http://www.educationcenter2000.com/debt_collectors/cease_desist_letter.htm
http://credit.about.com/od/debtcollection/a/ceaseanddesist.htm

(By the way, I'd be sure to reference in the letter that they have already broken the law by threatening to call your boss about the alleged debt.)  Just be sure to mail it via *certified* US Mail with a return receipt request, and save a copy of your letter.  If they contact you more than once after receiving your cease communication letter, then they are breaking the law and subject to fines for each incident. Though the call came from Washington state, I believe this is National Credit Systems, Inc. which is headquartered in New York. Here's their address:

National Credit Systems, Inc.
117 East 24th Street, 5th Floor
New York, New York 10010

Sending the cease communication letter is the very least you should do. But since they've decided to play dirty and make illegal threats, you need to nail them for it...and fast.  Retain an attorney and get some legal advice ASAP. Good luck.