American Credit Debt Recovery Are calling every week to collect debt for advertising services that I never received The advertising was supposedly purc

Company Called American Credit debt recovery (www.acdrcorp.com) are calling my father every week trying to collect the payment for some advertisement he supposedly purchased in 2010 from company called ubs. I''m his son, I spoke to a debt collector and she played the recording of the conversation with the sales rep from the advertising company. The rep did not mention the name of the product, did not ask my father if he wants the product, and at the end he asked my father which for of payment my father prefers, and my father responded that it doesn''t matter. The thing is that my father is not fluent in English, second thing is that we never received any invoice or contract from the advertising company. Now the debt collector is saying that they will put a lien on the company because my father did not pay. My father did not even know that he has to pay anything in the first place. What can we do about this, and what debt collector can do to my father?? Thank You.