The waiver/statement/document you signed that allows the creditor to garnish your wages without a court order is rubbish. An experienced and properly trained human resources or payroll administrator would laugh if such a document crossed their desk.
However, not all human resources or payroll people are experienced or trained and may be bamboozled by an illegal wage garnishment order if it is dressed up with intimidating legal language and arrives in an envelope from an attorneys office. I suggest you locate your human resources or payroll person and have a confidential conversation with about your situation. Ask if they have handled wage garnishments before.
In California, a creditor is required to file an Application for Earnings Withholding Order (form WG-001) and Writ of Execution (form EJ-130). A completed Writ of Execution will contain a stamp from the California court and a signature by a clerk of the court. An experienced human resources or payroll administrator will recognize an authentic Writ of Execution and will not be fooled by whatever document the payday lender will provide. (See the California Franchise Tax Board document Wage Garnishment / Earnings Withholding Order and Small Claims Forms: Collections (for Debtors))
Other states will handle wage garnishments differently, but the basics are the same: A court must order a garnishment unless the garnishment is related to tax liability or the repayment of a student loan.
Assuming for the sake of argument that a judgment-creditor begins the wage garnishment process, judgment-debtors can apply for an exemption. In California, judgment-debtors who are about to have their wages garnished should read California form WG-003 and then complete form WG-006 to apply for an exemption. Do so immediately -- a wage garnishment is much easier to prevent than unwind if you are exempt from garnishment.
I hope this information helps you Find. Learn & Save.