Who called from 3604601036

I too have received multiple calls on my cell phone from this number.  In all cases, my phone didn't even ring.  They have not left a message...

I got a call and didn't answer, they didn't leave a voice message.

I also let it go to voicemail -- no message -- tried to call back and got a busy signal.

Just got a call from this number. answered. No one spoke. I've had this call several times.

Got one for this #, same as others,

Hung up on me right away.
No voice mail.
Fast busy when I called them back.