Johnson & Pham, LLP

I received a certified letter from Johnson and Pham demanding $10,for items I sold on ebayI called them to explain my case and to tell them that I was not aware that the people that sold me the items was selling me counterfeit itemsI furnished the name and all contact info I had regarding this company as well as showing them how I found this companyI Google searched for cell phone cases wholesale and a website came up on top of the list, alibaba.com, I followed link and it took me to a page that showed all the cases they carried with prices, nothing looked out of place and all items openly showed the companies logos of all products being sold
The law firm told me that they were well aware of this company and that they are known to sell fake and counterfeit itemswell that's good for them because I had never heard of them and did not know that there were websites selling like thisI didn't go to some dark alley or china town looking to score fakesI purchased from what I thought was a real company
The law firm demanded that I send them any remaining inventory and that I provide them with a full list of anyone I sold toShould I do this and do I have to, can I get in more trouble for doing this? I stopped selling the moment I received the letter from them

They tried scamming me with a threatening letter and offering to resolve a issue with $10,Shame on you!!