due process violated child support

My son had a summons and warrant signed simultaneously even though the child support office had his address and all mail from them came to the right address. He owed 5500 in custodial arrears and 1800 in medical arrears. $5000 was paid this week. An attorney whom I contacted told me briefly , after checking in the computer, that these simulatenous acts were not right. He had to leave to go to court and I am left with the issues of quashing the warrant and taking care of the passport denial which is now below the $2500. There has been no change of address up until this past year . Hence, a summons should have been served and my son would have gone to the court and I would have hired an attorey had I known there was a court date. Child support office is refusing to cancel anything and more money was paid if my son had gone to court on an arrest.