Like most answering machines, mine is set to answer a call after the fourth ring. I have noticed that most telemarketing robo calls, political surveys, and charities tend to hang up after the third ring. I suspect that they do this to avoid paying for a call that goes to an answering machine.
My suggestion is to add an option to let the caller hear three or four rings before the call is ever put through. This would virtually eliminate nuisance calls at meal time.