Really?

I received a voicemail today on my work cell from someone claiming I needed to call them to complete something. I called this number and this person stated that they were with X and X associates and they had purchased an old debt of mine. Let me explain I havent had an unpaid or late paid bill since Jan 2003. I maintain a credit score of 795. This person claimed I had a card opened in the late 90s and claims on May 2003 I made a payment of X.XX amount and nothing since. I did NOT recognize the card holder and he stated the account had been sold multiple times. He claims I owed two hundred and something but now with interst its six hundred and something. I asked if this was truly my debt why I hadnt heard about it until now. He of course had no answer other than they just obtained the debt. He claims I SHOULD have received a letter last week which I did not receieve. I asked him to resend the letter and I would contact my lawyer. He stated he couldnt resend the letter and wanted to know why i wanted to speak to a lawyer. I told him that I wasnt aware of any such debt and wanted to know my rights. He sounded a little upset but regardless the conversation ended.
Do I need a lawyer? That was alot of years ago and I could search through paperwork if I must but would really like anothers opinion. ( I dont really have a lawyer...yet)