I have no clue who are they, calling and calling, never stop

Called twice within about three minutes, both times I said "Hello" more than once and never got a voice from the other end... Have no idea who it is but did this the other day also. Obnoxious.

Got a call from this number. They left no voicemail message so no clue who it was.

Northland Group. Collection Agency

Got a call didn't answer no message either.