My daughter had some guy calling her saying she kept calling him, he got pretty vile and left some rather disturbing messages on her VM, she only brought it to my attention after the VM and played it for me.
I researched his phone number, found out who he was, where he lived, where he worked and what car he drove etc.
I called him from my daughters phone and told him who I was and why I was calling, he started off being a smartass so I dropped a few nuggets of personal information about him to get his attention, I then explained that my daughters number had been “spoofed” and told him how that works, I also told him it’s probably a good idea to remove his personal info off of social media because that’s how I gathered my information about him, he apologized and we hung up.
About 2-3 months later he started getting people calling him and asking why he kept calling them, like he was doing to my daughter, he actually called my daughters number and left a 2-3 minute apology message about how he acted and what he said to her, this is how we know the same thing happened to him.