Collection Agency Anguish

I have been receiving collection letters from two different collection agencies, both of which list IDT Carmel as the creditor. I have never heard of such a company and cannot find anyone to speak to about the debt. I am receiving letters from a company called Encore and a company called Bay Area Credit Service, LLC. I have called both companies. Bay Area has no record of any account under my name, and can only leave messages for Encore. I do not have any idea who IDT Carmel is, or how to contact them. I need to know who they are, how much I owe, and why. I will turn this over to my attorney, but I do not have any contact information or account numbers. I am getting the idea that IDT is also a collection agency, from researching them. Why would I have two different collection agencies collecting a supposed debt by another collection agency??? Why does debt management have to be so difficult? It seems you make one mistake and no matter what you do to fix it, it is always there. Is it legal for multiple agencies to collect on a single debt? If I were to pay each company, I would pay for the same mistake three times! Can anybody help me? I would appreciate as much help as I can get!