Need Help ASAP!!! Goldman Roth Acqusisitions

I am hoping that I can get some guidence. My mother just rcvd a call from Goldman Roth Acquisitions and the gentleman started threating her stating that he was going to put a lein against my car (since my mother was also listed on my car) and that my mother needed to give up her last unemployment check to pay off this debt. He stated to my mother that she could go without for a month just so that the debt could get paid. He was very nasty with her. So I took it upon myself and called him and I asked him for a fax number and address so that I could send a letter and he asked what letter I said a DV Letter and I also explained to him that I know he has to validate the debt he asked me if I was a professional and when I said yes he hung up. In return he called my mother back and left a nasty message stating that I better not ever call there again and that their conversation was recorded (which he never told her that) and that she can't get out of this. So I guess what I am asking for is opinions as to can they lein my car and etc.

Please help