Pathetic service while my name has been ruined!!!

My account was used **********ly last year June and I have reported it so many times and even sent through all forms that they needed, sent those more than four times, yesterday when I went to apply for a home loan I was told Ackermans has listed me with ITC and when I called for atleast a letter to help me with the home loan stating that the account is under investigations and they told me they can’t help me. How do I solve this? Am going to sue this company seriously.