I actually just remembered that something similar was happening a while back. I was getting voicemails from some guy who was cheating on his wife. LOL. My phone never rang, I would just get a notification that I had voicemail. I called Verizon and they could not trace it back to anyone (or so they said) because he was not calling, he was recording the messages and then sending them, not actually placing a call. They eventually stopped but all Verizon would/could do was change my number, which I did not do.