Who called from 3604606392

Received a call this morning, did not answer, no voice mail left.  Number called, rings once and then gets a "fast busy" tone.  I believe the number originates from Bellingham, WA, no idea who/what it is.

I got a call from this number on my personal phone this morning, no answer, when I call back its a busy signal.  AHHHHHH

I also received a call from this number, I wasn't able to answer it though. No voice mail or anything.

also received call this april 4 am. checked on "who called us" .com and it is a data collection for Verizon. Checking to see if numbers are working and what carrier (ours is At&t).  they find this out from ringing.
reported them to "do not call list".  dr. pjc

Recieved a Call from same number & recieved same Busy tone when i called back. Highly suspicious:-\