Unfortunately I have found that these marketing calls systems use robot diallers that call blocks of numbers in sequence & test for a response before switching through to an operator muppet.
The secret to avoiding these calls is to lift the receiver & supress the natural instinct to say 'hello' leaving the line silent & within a few seconds the line will disconnect & hopefully get flagged by the robotic dialler as a 'dead' number.
Your regular callers will have to be made aware of your policy (& hopefully adopt it) so that they get into the habit of saying 'hi' first.
It is about a year since I adopted this policy & it has served me well, I occasionally get these calls but do not even have to spend any time explaining to a persistent phone line rapist that I am just not interested. 😉