Confused....

I know nothing about legal matters. The state social services department sent the payroll deduction things to my place of employment, and they sent it to corporate headquarters, where payroll is located. They were supposed to be withholding $100 a month for the child support, but I get a letter from my employer's legal department saying they will only be withholding $46.12 every two weeks instead of $50.00, because, their exact words, "Louisiana law prohibits us from withholding more than 50% of your disposable wages."
Guess when I go down for this new court date this Thursday, I'll take the letter from Sonic and show it to the social services people in the court and/or the public defender and see what they say about it. I'm totally lost, and want to make sure I'm not going to get into any kind of legal trouble!