If you were not served with a copy of the summons in time to respond, you'll need to file a motion to set aside the default and default judgment that was entered against you, (CCP 473(b)), making sure you attach your proposed answer, as well as request that the writ of execution be recalled and quashed. You'll need to do this on an ex parte basis. Beyond that, you need to contact an attorney
A proper response would require a thorough investigation into the history and background of this relationship. The information provided above is just that, information, to be used as you see fit.