William-
If you have caller-ID and don't recognize the number, you should NOT answer it because:
1. if it were "real" and was important, they would leave a message.
2. if it was a TELEMARKETER, picking up the phone confirms to the COMPUTER DIALING PROGRAM, that your phone number is valid and can now be SOLD to other marketers!
phone rang and I answered it. The voice on the other end was telling me that it was not a valid extension and then hung up. I called back and it is supposedly not a working number.
Unsolicited call and I am on the Do Not Call list. I didn't answer, but when I called back from my office phone it says the number is not a working number.