http://www.sdcourt.ca.gov/portal/page?_pageid=55,1554986&_dad=portal&_schema=PORTAL
As you can see, it mostly covers sexual or domestic situations. Business "harrassment" is called spamming, there is no law prohibiting that, because business interest would never allow a legislature to pass a law prohibiting excessive advertisement and solicitation.
You are better off seeking technical means such as call blocking. Google it and you'll find multiple means for different service providers.