In TOEFL test, my essay definitely does not exceed the word limit, or there is no clear standard about this~
As per TOEFL standards, an effective essay written for the TOEFL Independent Writing Task, which can score over 25/30 should contain at least 300 words. That is the minimum and there is no upper limit. Considering the time factor, I feel it is good to stick to the 300 word limit which is in no less no more mode :D
Nevertheless, from my point of view, telephone actually influences people's lives more deeply since it helps connect people more closely and raise the company's productivity.
Why do you talk about the productivity levels of companies? Let's look at your prompt;
Topic: Do you agree or disagree with this statement: The telephone has greater influence on people's lives than televsion has.
Your prompt is about the influence that telephone and television has on people's lives. There is nothing said about the companies, but strictly it deals with how they affect our lives. You should not go out of topic and especially in the introduction you should stay with the prompt very closely as the purpose of introduction is to introduce your topic in its real sense to the reader.