Who called from 4086040017

I keep getting calls from this number. Caller ID just states California Call. I let the answering machine take the call but they never leave a message!

Phone number appears with no caller identification. They leave no message. Two calls within the last hour.

No caller id (Out Of Area), no message left.

Three rings from no caller ID and no message left.  another website collecting unwanted calls has a comment that this is an "Energy Company."

The caller, called us @12:31, noon,02/18/2014.. My wife & I picked up the phone, but they caller kept silent.
Probably, it used different numbers to call us before & we told them" Do not call.". According www.800notes.com, the caller started calling people since 01/30/2014. When I returned the call 1st tome, no ring sound on the other end. The 2nd time, I heard some noises , but no one answer.