Folks, this is what caller ID & answering machines were made for. Before I had them, I used to get all kinds of calls to my business number from people trying to sell me something I don't need. Now, with caller ID, if it shows "unavailable" or "blocked" or "private'I don't bother to answer it at all. If the caller hangs up after the 3rd ring, it was for sure some salesman dodging the answering machine & the long distance phone call. If it was a potential customer, they usually leave a message.
Few things are harder to put up with than the annoyance of a good example.