Help, my friend is being stalked

My friend (26F) has been stalked by this guy since middle school. She has repeatedly rejected him and told him to leave her alone, even blocked his phone number and moved. Last time I actually saw him was when we were in high school when she rejected him again, then sporadic updates like him finding her on random internet sites & making new profiles to DM her but nothing more. We’ve both moved to different states since high school.

Recently he started calling her again, no caller ID, unknown number so she can’t just block it. He’s called her CONSTANTLY. Like, 100 times in an hour!! He hasn’t sent any messages, just calls her constantly.

He claims to know where she lives.
I’ve told her to make a police report and start keeping records. What else can we do?