When you receive a robocall, chances are someone like Nick Palumbo collects roughly $0.0024 a minute. Those fractions of a cent can add up to millions of dollars. Mr. Palumbo accumulated more than $3.2 million on the hundreds of millions of calls routed through a telecom operation based in his Paradise Valley, Ariz., home last year.
Two phone companies run by Mr. Palumbo are among dozens of little-known carriers that serve as key conduits in America’s telecom system. But the rise and fall of those companies also illustrates…