Legally, interest can be added to a CS arrearage.
What was the original amount of arrears, without the interest added?
How long had the arrears been owed?
However, quite often the NCP wins in court when they have faithfully made payments on the arrears, were never told what the interest is, then they think that have it paid off, just to be hit with a ridiculous sum in interest.
If you wish, you can hire an attorney, but it might be a waste of your money since the state attorney will be in court anyway.

