To get an internship at goldman sachs you must know some people, so your friends probably went to eton and got some connections or something like that. For us lonely peasants we have to work hard for our salaries.
Based on my experience, working at some no name accountcy firm or one of the top 10 in the country, you might see a few extra thousand a year but nothing realy in line with the preportion of the size of the company that you work for. That is why small firms are often better for IT because you get paid the same and do less work.
These big firms have more staff members per IT support person and they definitely don't pay better.
But you are comparing apples and oranges. some telecoms support person and some IT support person are two different jobs. Telecoms support is like customer support and goldman sachs support would more technical etc.