its rude to turn up uninvited in my world !
I spent years turning up uninvited on farms, it was my job.
Fortunately the great majority would accept a polite introduction, it was up to me to read the situation and decide how to make the next visit/appointment. But even back then there were a few full of their own self importance.
Even if you are busy when you receive an uninvited caller it doesn’t take or cost much to say leave me a card and give me a call on the phone to arrange a more convenient/appropriate time. It doesn’t hurt to be nice to the little people. You may find that some progress and succeed and that you might need them in years to come ....