Who called from 6506444123

This # call and when I answered all I got was a dial tone.  I call back and only got a dial tone.

TELEMARKETER!

they called, left no message.  I called back and a guy said "hello" and I hung up.  Don't know who it was.

I get calls from 650-644-4123 - No Name all the time.   They never leave a message on the answering machine!  Is this a real number?  Does anyone know who this is or how to stop it?
This should be a crime...
Jim

Called on 05/31/2013 at 07:32 PM from Palo Alto, CA. Caller ID also shows Palo Alto. No message was left, so at this point no one posting here has any idea who this caller is. I've gotten calls from palo alto before, but I doubt it's the same caller as this # has only been reported for the last few days.

I received a call from phone number 650-644-4123 and it says that it is from Palo Alto CA.  I received it at 3:16 PM.  I am on the Do Not Call List and I still get calls like this. My guess is that it is a telemarketer. I know no one in California so I refuse to answer their call.