Federal senators and representatives have a service that handles all of their correspondence. I've gotten a reply before that was on a subject completely different than what I had written them about. I've also gotten an identical letter as my in laws have when they've written on similar subjects. It's all form letters. It use to be that a letter carried some weight but now it is about volume pro and con. E-mails, letters, calls, etc...
I've given up on writing and now call directly. I identify myself by name with my full address and advise that I am a registered voter. At least that carries some weight with the staffers that answer phones.
I can say that I've had a staffer call me directly before regarding a letter that I sent so maybe it's not all worthless effort.
Now at the state level. I have the cell number for my state representative and speak to him on occasion. If something comes up that I feel needs to be looked at I am always free to call him. IMHO we've lost D.C and the best we can hope for is to keep our states.