Before a creditor or debt collector can garnish your wages, it must sue you and you must be officially notified of the lawsuit so you can respond and show up in court to defend yourself. However, there are instances of people who are not properly notified and who then get judgments against them and have their wages garnished. It sounds like this may have happened to you.
I recommend that you immediately contact a consumer law attorney who helps people resolve debt collection problems so the attorney can sort out what has happened and recommend a course of action for you to follow. It may be that you have grounds for a lawsuit. Your first appointment with the attorney should be free. Find out how to get FREE or low cost legal advice about debt collection from a consumer law attorney here.