Enrique - Please contact the New York State Attorney General's office right away. You may not be aware of this, but New York Attorney General Andrew Cuomo filed suit against 35 law firms and two debt collectors in New York State in order to throw out an estimated 100,000 default judgments improperly obtained against New York consumers.
I don't know if the firm that obtained the judgment against you was included in that action, but you should check immediately. You can read details here: