Who are these people?

I googled phone number of this company and my own name after receiving a very rude call from them. It's obvious the company pushes the law but how do I find out what they are accusing me of owing? I have never received a statement and they won't tell me anything unless I tell them my full name, address, SSN and birthdate. If I owed someone, wouldn't they have that info already? There are too many thieves running scams so I won't give out my information just because someone asked for it. I can't think of anyone I haven't paid, unless it's a bill from a rehab hospital that workers compensation was to have paid 8 years ago and I told the hospital I would NOT pay because I was severely injured and unable to work for a few years and workers comp or my employer had the financial responsibility. I used my 401k and personal savings to get by until I found a disability attorney and he asked the doctors and hospital for ALL bills and marked them paid in full.