Wow. I am an HR rep, maybe I can jump in here.
First of all, in all states in the US wage assignments are legal. Unfortunately, it IS indeed up to the company whether to honor them or not. My husband has the same job as I do, but at a different company. His company Does not honor wage assignments unless they are court ordered. Yes..There are court ordered wage assignments, not to be confused with garnishments, but rarely if ever are they on a consumer debt, and I won't get into those here..My company does honor them, however.
Here's where things get tricky and unfair. Ok..If I got a wage assignment on an employee, I AM NOT required to notify the employee. I can simply deduct the monies and give them a smaller check. I would not do that, because it is not ethical in my opinion, but lets be honest..If I was doing payroll and cutting checks for 2000 people, I might not be able to notify the employee of the assignment.
It is always always always your right to revoke the assignment. You know what? In order to revoke one, you don't even have to send a copy to the PDL. It's not important! As long as HR has a signed and DATED letter of defense, a PDL does not need a copy. Period.
I am shocked that this assignment is being broken up. That's unusual. Yes, you can surely attempt to revoke the remainder..But I don't know how your HR dept payroll system is set, you may not be successful. Also, I think an attorney is a huge waste of money, because these things are legal.
Sorry to ramble. If you have any detailed questions, please pm me. I definitely sort this out for you, especially if you can describe the assignment for me.