"Thank you for your thoughts on this matter, I didn't read them. Here is a boilerplate statement espousing all the great things about this bill that you specifically criticized in your message to me. Please don't reach out again."
Enough phone calls will make a dent, though. I worked on Capitol Hill and every office is just a handful of young staffers manning the phones. So when we pissed people off, we really felt it. Those days were the worst. Couldn't do anything except answer the next ringing phone. You can definitely motivate action that way, but it takes a decent little group of people to be willing to make the calls.