Friend of the Court I've paid, went to court & took custody of child. Please fix my case Detroit, Michigan

My ex used a third party to collect child support when she left the state of MI.  They collect $335 monthly from my pension until I took custody of my son in 2004.  I thought my  Friend of The Court case was resolved when submitted documentation to show payment in full and they reversed child support so she would become payer.  Some how 9 years later FOC has not zeroed out my balance continued to add a debt to my child support each year. They closed her account out without her paying out 200 over 5 years.  The third party which collected the payments from me has also wrote FOC to verify the amount I paid they received from me. I have submitted all the required documentation 3 times over the last couple of years. i hired a lawyer to resolve this affair and it was handed over to a referrer to audit my account, but I am still waiting.  I even came to Detroit and hand carried all the documentation and left it with a FOC window rep which was one of the rudest people I have ever met.  I am still being effected by this on my credit rating.  This is crazy and very unfair.  My son has left home joined the military and I am still fighting to get this mess corrected.  How is this possible?  Please Help me!!!!!