This contains only legal advice

See the definition of harrassment and remedies in California (assuming that's where you are)

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.