Called and left no message.

robotcall regarding home owners septic system.  Claims not a sales pitch.

Couple of calls every day for last 2 weeks -- we don't answer ANY calls from a  number that's not familiar.

let the answering machine pick up the call and caller hung up

i received a call from (530) - 324 - 2385.  no one was on the line when i picked up and i couldn't call back.  isn't this illegal?  i can't call the number back and there's no way to opt-out of calls.  i thought a law passed several years ago provided options for consumers (or in this case call receivers) to follow up pro-actively.