I've gotten those calls too....just annoying when your trying to get things finished up...answer and hang up is what I do when I'm at the shop....my cell if it's not on my phone I just don't answer it...Robo calls are just that. Robotic.
Set a program and it will progress sequentially through all numbers in the range defined.
I was receiving calls that were Bots. The audio sounded human, however deviating from the expected dialog would end the call.
When asked if the caller was a Bot the reply always ended in the call being dropped by the Bot.
A human would be able to reasonably reply to a basic/complex question.
That is when I went silent ring.