I don't call my House Rep's office very often and I never call my Senators' offices (Joker McCain and Killer Kyl). I have called a few other Congressional offices.
My experience is that the people on the phone do not use that contact to find anything out about my opinions (other that the short blurb I have prepared) nor usually where I reside. It really seems a waste on their part, though, perhaps, they don't care what the callers think. Which is most likely the case. A trifle shortsighted perhaps.