Calls multiple times, no messages left, when I attempted to call them back it is a non-working number so obviously a masked computer generated call.

Unknown source of number, when I call back, I get an error message ("your call cannot be completed as dialed").  No message left, multiple calls.

Called twice today but left no message on voicemail.

I called the number twice and got a recording each time that the call could not be completed as dialed. I suspect this is a spammer spoofing a non-working number. I've blocked the number.

Missed call from this number. This is not a valid number to call back. I'm also blocking this number.