Okay, kiddo, so have you ever been around a bunch of kids who aren't being very nice to one particular kid? They might tease or pick on them or do things to make them feel left out or scared. That's kind of like what mobbing is, but with adults and phones.
Sometimes, a person might get a call from lots of people all at once, or one after the other, and they might all say mean things or try to scare the person. This is called a mobbing call, and it's not very nice.
Just like how it's important to be kind to others and not bully them, it's important for adults to treat each other with respect on the phone too. If someone gets a mobbing call, they should tell a grown-up they trust and get help to make it stop.