ITC records

I had a contract with cellc and couldn't pay it but when I got a new job i paid all the money i owed them, the account was handed over to one of those collectors company so i paid through them, now my issue is even after 7months cellc still listed me on ITC records that i owe them. I trued numerous times to call cellc but their call center consultants could not help me. I have paid up letter with me. Cellc please remove my namr from the ITC as i do not owe you anymore.