They keep calling me from this number. When I pick up, I hear background noise but nobody says anything.

I never answer unknown tel. numbers any more. Never had many robo calls on landline.
But since switching same phone # to cellphone, I constantly get these crank/spam calls.
Only have a flip phone and am limited to "silent" and reject options.  Seems these calls
come in every two weeks in droves then let up some.  Do not call list is useless to me.