This person called several times this week and never leaves a reply.

This number calls once to twice a day and hangs up when I answer.

These guys call me mulitple times per day.  Just a few minutes ago, when I was on another call for about 10 minutes, these annoying folks called me 3 times when I was on my other call!  I called them back & after a few minutes of hold music, Scott answered.  When I started to make the request for him to put me on the do not call list, he hung up on me.  I called back again & got a prerecorded msg about education opportunities, with keypad options.  I used option 3...do not call list.   Rude company... made a note of the #.  Next call, they get the whistle in their ear!

Refused to take my cell # off their call list

Probably time to buy a call blocker device, app, or phone.
Google "call blocker" to see the various types, and find one that best meets your needs.