National Recovery Agency Sending bad debt to IRS- Credit card opened fraudulently Riverside, California

I received a phone call on my cell phone from this company. They stated that the needed to confirm my name and social because they were sending a collection to IRS as a bad debt. After speaking to rep and explaining that the debt was fraudulent because i never opened credit card account, and asking why i had NEVER been contacted before now; the response was that 21 letters had been sent to address on account. Well, as I had already explained that it was fraud and i didnt live at that address so how who i ever know to respond. i was told that now the IRS can now collect on bad-debt write-offs. WHAT?!?!? Now this debt never showed on my credit report which i pull every 2 years, they claimed it was charged off in January 2000. I have never received a phone call til now; and when i demanded the tell me where they got my phone # from, i was told until i act like an adult and take responsibility for my debts they would not talk to me then they HUNG UP. Now here's why i wantted to know how they got my #; you see my cell phone is in my fiances name and social therefore not linked to my former married name; i do not list it on any social network nor do i give it outfreely. So how the hell did they get it? I called back 4 times and everytime the agent heard my voice he hung up. What do I do now? A fraudulent charge is being sent to IRS. and since when is this okay???