Handing over paid up account without notifying me that I owed money on a closed account

I am beyond LIVID!!!

I paid up my Edgar's account about a year or a year and a half ago and all of a sudden this week I've been called by Shapiro Shaik attorneys. Imagine my surprise when I see that not only do I owe money to Edgar's on my PAID UP account, my credit score that I've worked really hard to maintain has been affected. I never receieved anything stating that I owed money. Edcon messed up by not clearing the balance when I paid them and TCS messed up by not notifying me on this alleged money owed