Legal Question in Civil Litigation in California

Just because a law firm represents a client in one case doesn't mean it will represent that client in every case. Thus, the company must be properly served in any new case. I am a little confused why the law firm would want your communications, but wouldn't accept service. Based on your question, serve the contractor and don't give the law firm any information until it is officially representing the contractor. Is there a reason you would rather serve the law firm rather than the contractor?

The law firm is a bit mixed up as to the communications. The rules of ethics prohibit a lawyer from contacting an opposing party who they know is represented by counsel. But nothing prohibits the parties from speaking to each other. I've even seen cases where both sides were represented by counsel, but the parties met and settled the matter on their own.

As to service, the law firm has the discretion to refuse to accept service. That is an issue between them and the company, who is their client. So you are going to have the company served.