Takhar Group Mike??is trying to collect for a book club, to whom I don't owe anything and know nothing about Internet

The Takhar Group has been harrassing me for almost one year.  They say I owe them money for a Columbia House account.  I do not owe this bill.  I asked them to send me a signature on a contract or a bill, to prove that I owed the bill. He just keeps saying I owe the money and I need to send it immediately or they will take action very soon.  I have hung up on him and told him I was going to call my attorney.  Does nothing scare these people?   He called and told my husband that He had to give the phone to me because he demaned it.  Very pushy and rude. 

I get an 800 service number on my phone.  800-620-0371 and he said his name was Mike.  They also have an internet site.  TheTakharGroup.com