Those of you that let the calls roll to your answering machine, voicemail or worse yet answered the call you have just ensured you will receive more of these calls.  Maybe not from the same number, but they’ve just identified your number as valid which assures more calls of these 'faux telemarketer calls'.  (I call them faux telemarketer calls as they are generally not legitimate telemarketers, but simply scams!)  Most of the initial calls originate from software (aka; ‘robocalls’) – once your number is identified as active, then a real person may be there on the follow up calls.
If you have the capability to ‘BLOCK’ the number that called – that is the best action.  Since 2010 I have logged and currently block nearly 600 of these nuisance calls.
If you don’t have a blocking option, keep a phone with caller ID close by and simply hit ‘talk’ and ‘off’ simultaneously.  This will reduce the number of nuisance calls, but not stop them.
If you really want to block them – in addition to a number of cordless phones available there is software that a layman can install.  Of the over 500 calls I’ve blocked, I've only added 16 over the last 3 months.  (Most of those are from a new series of numbers that were not previously blocked)
So the message is simple – blocking works….  Using the aforementioned processes I seldom have a second call from a given number.  But, when I do - I love it when "Number Blocked" shows on my 'Caller ID!!!  (When they call repeatedly it causes me to wonder about how stupid some of these dummies really are!)
Additionally;  The Area Code, Exchange or even the entire number displayed on your caller ID probably does not accurately reflect the origin of a call as many of these crooks use software that disguises the originating number.  (I've actually seen numbers reflecting my own Area Code and Exchange)
PS:  I think Call Notes should add a 'Call Type' for 'Spoof' or 'Scammer Calls'!