How can I dispute this service with the courts?
If the lawsuit is valid (even though you dispute the matter at hand), fighting service is a waste of your time.
You'd be better served to fight the case, rather than the service.
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From YOUR CA court website:
In "personal service":
The server gives the papers to the party being served.
It can be at the party's home, work, or anywhere on the street.
The server has to identify the party being served and hand the legal papers to him or her and inform him or her that they are court papers.
If the party being served does not want to take the papers, they can be left on the ground in front of him or her.
If he or she takes the papers and tears them up or throws them away, service is still considered to be valid.
The person being served does not have to sign anything.
The server then fills out a proof of service, detailing when, where, and how (in person) the papers were served.
The server signs the proof of service and returns it to you to file in court.
Personal service is complete the day the papers are served.
"Personal service" is the most reliable type of service because the court knows for sure that the person being served got the papers and, if necessary, can question the process server about the "service."
Since it is the most reliable, "personal service" is valid in all types of case.
Also because it is so reliable, it is generally required when serving the first papers (the petition or complaint) in a case.
Service of Process - getting_started_selfhelp
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A CA licensed bankruptcy attorney chimes in on personal service:
Improper Service of Summons and Complaint in California
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