Global Solutions Calling threatening to file suit against me for payday loan I never took out in 2011 Chicago Illinois

I have had these people calling me for a month and then started calling my son's number (to which I have no clue how they go) stating I took out a payday loan from a cornerstone LLC in August 2011 for 310.00.  I called back had 5 people hang up on me and the three people I talked to had different stories.  They are threating to file a lawsuit against me for $310 that I supposedly borrowed.  One said I borrow more and the balance was $310.  I am sick of these people calling me.   What do I do about this.  I told them to send me paperwork and they said they already had.  I told them I never received it, and they stated well they had sent it once and couldn't resend.  That to me is a scam.  If I truly owe money to someone they should provide me with written information of what they are talking about.  I have never had someone flat out tell me no for something of this regards.  Anytime I ask my bank for something I am immediately given it.  Someone needs to stop these people.