It's a robocall that sounds like a human. I've gotten a call a few times and they've used different voices. They said something about a cruise line and then waited for me to say something, said "are you there?" when I didn't respond, and when I said yes they repeated their opening line in the exact same voice. I actually thought it was a human until they started replaying their lines.

The second time they called I asked "are you a robot?" and the voice said "yes, I am a real person." I said "no, are you a *robot?*" "...Yes." (in the exact same tone of voice as their earlier "yes.") Eventually I was disconnected.

I gotta say the whole thing seems a little unsettling....