Whenever a call comes in that we do not recognize as one of our regular contacts, we just look at the caller id and ignore.

Later, we go into our Verizon settings and add the number to the call block list
One of the problems that allows people to get scammed by crooks is that one should remember that if you have not entered into any sweepstakes, or applied for any credit, or shopped at any store (whether online, or in person) where you applied for their card or gave your email or phone number, then you are going to be scammed, spammed, and/or conned, for maybe all of the above.

The rule of thumb is that you know whether or not you have requested contact with the number that is calling or not.  If it is not family, work, business related, emergency from your doctor or hospital, "Do not pick up" or answer.

When you answer the phone, you are confirming that your phone number is a valid number.  When you select the option in an email for them to remove your name from their list, this allows them to remove your name from one of their lists and pass you on to another of their lists or list of associates.  In other words, you are setting yourself up for indefinite contact from a multitude of partners. If ignored, eventually they will go away.  It may even take up to a year, but eventually they do go away, because your phone number of email is not a prospective investment of their time.
Also, if you allow it to go to voicemail, that too, assures them that your number is valid as you have pick up message on your voicemail.  By doing this, you allow them to harass you via voicemail as well, even though this is voicemail, eventually, this will become full and you will not be able to get important messages left in your voicemail.  Just ignore the call.