There are provisions under which Congressmen or Senators can request addresses of veterans. It goes through a clearing process to protect privacy rights, but there are conditions.
Our privacy laws also allow representatives to represent veterans if they approach politicians. So if I write to you to say, “I'm having difficulty getting my claim for any of these services”, as a politician you are then empowered to act on my behalf. Politicians frequently contact us on behalf of veterans, and we work through their representatives.