had a 4 min long blank voice message from this number...someone tell me whats happening

First call so far from this number - no answer or voicemail.

213-000-0000 called.  No one on other end.

This seems like it was dialed from a main switch. Someone tapped in as an operator and dialed my number. The 'no voice' is probably testing. The scams are people who have tapped into the line. Yes, this can work with cellphones too.

i just started getting calls from this number i have had about 6 in the last 45 min, i told them finally i was on the phone with my brother and if they disided to talk call back  they have not called back i put them on hold and they stayed there for over a min then hung up why is this calling and who is it i dont understand