A report is a presentation and analysis of findings and data from practical research, aimed at investigating, exploring and sharing specific information. Meanwhile, an essay seeks to answer a question based on research too, but through the writer's own point of view, to support his own conclusions.
Taking this into account, we may say that <em>annoying people on cell phones</em> is a topic more suitable for an essay.
The reason that does not make a case for the value of proposed solution is that "it is effective in solving the problems." As always, the simplest explanation is the usually the best solution. This reasoning is lined with principle of plurality and the principle of parsimony.
I phoned him because he was not home.
The second part of the sentence is now dependent on the first as it cannot stand alone as its own sentence.
