I picked up and said nothing. After a second, a computer voice said, "Goodbye." Presumably the program had already recorded the speaker's voice, but not in this case. This is a scam and likely a spoofed number. Proceed with caution. If you get an unknown caller and are tired of letting them ring and clogging up your voicemail, just say nothing. It's easy to tell the real from the fake, and almost all of it is fake with nothing to offer you.