People are always harassing my friends by texting and calling.

Hello, whether you know it or not, there must be a reason first. You are not a party, so you may not know the facts. The harasser has no special function. He won't know your friend's personal information for no reason. The reason is that we can't know. Maybe your friend is targeted by someone with ulterior motives, or maybe your friend has offended someone. You may know him because he is afraid to speak, or maybe he is afraid of being caught.