Even after years of paying off my child support I ...

Even after years of paying off my child support I have to deal with them. Earlier this year I refinanced my home and was delayed because their was a lein on my home from Child Support Services, when I finally got a hold of someone they told me that someone just failed to do their job.
Yesterday I received a letter saying I was going to be garnished $750 a month for unpaid child support, they told me if they were sent any funds they would just send it to me, I had to tell them to submit the proper paperwork to stop it and email me a copy of the proof child support is paid in full so I can also submit it.