Legal Question in Civil Litigation in California

If you cannot get the defendant to drop the case against you, you should file an Answer or Motion

You should still consult an attorney because you don't want the suit to go to the point where a default judgment is brought against you. If the action has no merit then your attorney can file a demeurer (it basically says there are no grounds for the law suit against you).

You should immediately speak with the plaintiff's attorney, or the plaintiff if there is no attorney. If they won't withdraw the service and acknowledge that you are not the defendant named in the lawsuit, you will need to hire an attorney to either file a demurrer (arguing that there is no basis for a claim against you) or a motion to quash the service (arguing that you are not the person named in the suit) (or both). If you do not take some action to protect yourself a default judgment could be entered against you.