Direct Merchants Bank I closed my account and they sent me a bill for over 7,204.32.They sold this account to a collection in 2011.

I had a direct merchants bank credit card. I paid the bill and had no charges on my card. I then closed the account because the interest rate was too high. Direct merchant bank sold this bill to a collection agency on november 11,2011. I just received a notice that i owe direct merchants bank 7,204.32 and i received this letter on january 7,2015. As far as I know I did not have any charges on this account. I do not have any documentation because I did not think i would need to keep any. I need to figure out how to contact direct merchant bank to settle this matter because i know i cancelled this account.