Revoke letter and notice of defense question?

I sent a wage assignment revoke notice to a lender and a month later they sent my employer a wage assignment demand and sent me a letter telling me to send a revoke letter to avoid wage garnish and I must fill out a notice of defense.

Attached to their letter there is an Affidavit of Defense which look like this "I, _________, hereby (swear)(affirm) that I have a bona fide to the claim of _____, which claim is based on a debt contracted on the ___ day of ____, 2009, and for security on which debt wage assignment was executed."
Questions:
1. Why are they asking me to send another revoke letter. And why are they still trying to place a wage garnish on my pay after i revoke it. (no, they haven't sued me and we haven't gone to court yet.)
2. Is Af