Definately
revoke that voluntary wage assignment and if you fax it to payroll, get the confirmation sheet and call to verify they have it, documenting the name of the person you spoke to. And I would do it your next working day.
Also, close your checking account and see if you can get a new one and DO NOT under any circumstances, give them the new number!
Finally, to the person who has paid back $1000 on a $200 loan: demand that your account be marked PIF with an $800 refund, or you will file with your state's attorney general!