I would hesitate to say that individual emails scare politicians, but if they are from somebody identifiable as living (and voting) in their districts (or states, for Senators) they do stand a slightly greater chance of being read by somebody on the politician's staff than a generic petition (normally treated as spam). If the letter/email is well-written and clearly not a form, even better. Phone calls, though, are questionable; some politicians treat calls that don't agree with their positions as crank calls and (as one in my area has been reported to do) threaten to have callers prosecuted for harassment or worse.

Having been on the receiving end of a change.org thing some years ago, I can knowledgeably state that 1) they are spam, sometimes verging on a denial of service attack; and 2) they often have nothing to do with what you, your employer, or even the law governing you is interested in or capable of doing anything about. Change is great, but it has to be something that (in a government agency) you're authorized (by law) to do. The agency usually can't change the law - the petition needs to go to the legislature for that to happen.