Diversified Collections INC Diversified Collections...called @ work, says I owe "a bill" and won't tell me what it is! Livermore, California

It started like this: I got a memo from the secretary at work to call this # about "business."  I called "Serena Baylor" and she told me that I owe a debt.  I asked her what it was; she said I first have to tell her my complete social security #.  I tell her that I won't do that--that's crazy, these days--and she then wants the # on the account on the "letter."  I tell her I never got a letter; then she says (again) that she'll need my social security #. 

I state that if I owe something, I need to know what it is.  Well, she says, she can ONLY give me that info if I give her the social.  I refused to do that, and told her to NOT call me at work.  I asked for her manager--she gave me his #, which led to a voicemail, which states to list your home phone #, your work #, your cell #, and your social security #--and to say everything twice.  I tell him (on the vm) my name, my home phone, and that's it--asking him to call me to tell me what the debt is.

I didn't get a call back.

My SO and I both called numerous times after that.  They absolutely will not budge. Therefore, I supposedly owe a debt, origin/amount unknown, and am supposed to pay it, but won't/can't bc I don't know how much/to whom.

Here's the KICKER:  I looked them up online (before this website came up).  I notice they mostly collect student loans and taxes--NEITHER of which I am in arrears.

I called the Federal Trade Commission, who advised me to send a certified, return-receipt requested letter demanding the original debt letter AND to cease phone communications with me.  I promptly did that, but after seeing on this site how these scumbags are, I'm guessing I will not get a return receipt OR a debt letter.

I checked my online credit on all 3 reporting companies.  All is in good standing at this point, as it has been for yrs.

Still, I am more than a bit nervous about what could be going on here.  What do I (allegedly) owe?  Or, what are they saying that i owe?  My identity MAY have been stolen (3 or so yrs ago, out of a computer data base on the West Coast)--did someone use my # to get a loan?  If they did, wouldn't that be on my credit report (which is attached to that social #)?  Did my lowlife vindictive ex-husband use my social (after the divorce, 10 yrs ago) to obtain student loans on my name/number?  IF he did, though, wouldn't THAT have shown up on my credit report?  Am I worrying for nothing?

SCUMBAG DCI!  Here I am, paying all my bills, doing my best to stay on top of financial things, just SO that I can have good credit AND not get dunning calls/letters and not worry...and there they go botching it up with a stupid phone call to my job.

But tell me this:  some of you talk about taking them to court if they don't follow the letter of the law.  So, if I don't get a return receipt, debt letter, or any other response....can I legally pursue this?