"Mr. Smith" is clearly a fake name, and, under the FDCPA, he is required to provide you with the original creditor's name, the address of his collection agency, and, upon written request, he is required to verify the debt within 30 days. He is also required to cease calling you at work if you've informed him that he is not allowed to do so. Plus, have you inquired about this "case number"? Is it even real? Contact the court where this so-called case if "filed" and see if it is legitimate. One final point - I googled the number you provided, and it shows up as a cell phone in/near Anaheim, CA. This is obviously a scam.
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As stated in the prior answer, this is a clear violation of the FDCPA and would subject the collector to a claim by you for damages. The problem appears to be knowing who he is and for whom he is working. It would also subject the lender to such a claim, but they aren't identified either.
The above answer is in general terms, and is not meant as legal advice. In order to fully answer the question, more information would be needed.