Child Support Letter.. super annoying.

I KEEP getting the same letter from Child Support saying they cant locate my BD

We were in court about 5 or 6 months ago and it was determined he wouldnt have to pay child support until he got a job or on disability since hes 'sooo injured' with his fake injury that cant be proved so he wont ever get disability but wont ever get a job because it 'hurts too bad'. YET he just signed up for school. Which is great, except he told the judge he couldnt even get out of bed, he was in SO much pain so he can go to school but not work. i guess i could bring up the fact that now that hes able to go to school twice a week. a part time job should be NO issue. End of side rant.

Anyway, They keep sending this letter. It was already determined by a judge that he didnt have to pay so I dont get why they keep sending it. Ive already contacted them twice with his last known address.
Its just annoying.