How Do I Quash an Order for Medical Support?

Iowa- I recently signed a document stating that I would provide medical support, for a child who is primarily in my home. I requested a hearing with the child support unit, and was told by a lawyer when I got there, that I had no choice but to sign and agree to provide the medical coverage, or it would be withheld from my paycheck. I signed, but took steps to get my son's medical switched over to my household ( his father and I have joint legal custody). According to the lawyer, Iowa law states that whoever gets the medical card (state medicaid), the other parent must provide the medical. Even though I cooperated, until I can get everything switched "on paper", I still received a letter stating that my employer had been contacted to place my son on my employer medical. It is expensive, and I didn't even get an opportunity to find something more affordable. I want to "undo" this paper I signed, because my son lives with me, but I keep having to jump through hoops, and am being told that if I file a suspension order, if I do it too soon, and it is denied, I will have to wait 2 years before I can request it again. It says I can file a motion to quash, but I'm not sure if this is the same thing. What do I need to do? I'm so stressed out, I can't think straight! HELP!