I got two calls from this number, the second of which did not let my cell ring more than a second. I have no idea who it was since they left no message in my voicemail and I don't answer such calls.

Received call.  Did not answer.  No message left.

Who are these strange companies who call cellphones at random.   How can we stop this nonsense and report to authority

Here are two pages of links to (mostly government) sites in Canada and the USA were you can report those scams, or learn more about them.

Look here first:
http://800notes.com/arts/I2neMkbUAAo/where-to-report-phone-crime

If the reporting site you wanted is not in the above list, try this one:
http://phonehelp.2truth.com/complaint_sites_rev.html

Consider buying a call blocker from your favorite store if nothing else works.
http://gg.gg/blockers