They threatened me saying if I don't call them they will take actions and will go against me.
But I don't know what did I do or why do they call me for and they didn't clearly explain who are they.
Relax Elizabeth, you've done nothing. This is a well known SCAM. Ignore the call, BLOCK the number, and never answer calls from persons or numbers you don't know. Here is the real IRS information on the scam:
Got call from this # also. They said since they had sent a letter and it was returned to them and because I did not return a previous call that the irs was suing me for intentionally trying to defraud the irs on tax returns. Told me that proceedings had been started and that I would be arrested and all assets would be frozen and liens placed on everything we owned. When I asked what address they sent the letter to it was to an address in New Mexico, I live in Iowa. Conversation got very ugly after I informed them I had called the IRS to see if this was a legitimate call. He thought it was awful that I would question his integrity. Never had such an infuriating call!