what SHOULD be happening is that the representative in question and/or their subordinates should be taking note of the received calls and the grievances.

the rep should then be using this information to know that a significant chunk of their constituents(with the votes that put them in office) disagree with policy and use this support to take the issue to higher places to be discussed and hopefully changed for the better. if this gets ignored by enough people that file complaints that rep might have issues getting support in the next election cycle.

in practice this doesnt always occur, but this practice should not be phased out as its one of the few manners the common voter can still interact with politics outside of voting.