It appears that the law office is suing you for the debt, I would suggest you get some legal help with this right away as you need to respond within 35 days.
Entry of Default – If a defendant does not file and serve a formal answer (with or without counterclaim) within 35 days of service, the court may enter “default” against the defendant, which indicates that he or she is not permitted to file any defensive pleadings. This is the first step toward obtaining a final judgment by default.