Complaint Review: ACS Legal Services (says law firm)

Daniel Christian called my cell phone and place of employment 4 times in 4 hours today. He disclosed a business name of ACS Legal Services a.k.a. A law firm in California. He says that he is a legal representative and that he has a legal notice pending in his office for me. Daniel with a strong accent says that if I do not comply and meet the demands of the debt today that I will be sorry. He mentioned that he has all my personal information to include my social security number. I asked for documentation. He refused and said that if I don't agree to make a payment by phone that he has all of my employment information and knows where I live and that the authorities will come and arrest me. I asked him to send me the legal notification and to stop calling. He refused and said no he will not stop calling and that he will continue to call and hung up.