I don’t know how it is in other countries, but in the US the offices of the politicians have to organize all of the feedback to then share with the representative. For example, if I call my rep’s office to say that KOSA is bad, they have write that down and aggregate it with anyone else who called with an opinion on KOSA to keep the rep informed.
When politicians’ offices are getting “spammed,” what they’re hearing is a collective message to act one way or another on an issue. That’s the part they act on.
My expectation is not that I will get on the phone with my rep. It’s closer to voting where I just need the recipient of my call to log my opinion so that it can be tallied with others who called about the same thing.