They keep calling and calling, always changing numbers. Recently I started receiving calls from this number but they never left a voice message. It is a clear scam or prank.
I always pause before I speak when I don't know the number. There was a soft beep after I picked up, and I heard a distant half of a hello. I said the company name clearly and "can I help you?" after the line went quiet but I could still hear something on the other end (could have been an echo of me). I hung up on it.