I got a phone call from a number that belonged to my professor at the time (I went to a tiny college and she gave her number out to her specialty classes because if we were going to be gone she wanted to know so she could cancel classes. Nothing creepy about that).
I answered assuming she’d let me know to not come to lecture the next morning. Instead it sounded like static, crackling and such, then suddenly the sound of what could only have been a barbershop quartet began to sing. I don’t remember the song except that it talked about your face shining so bright and I can’t wait to hold you tonight, or something. It was horrifying. I screamed and hung up the phone fast. I asked the professor the next day and there was no log in her phone that she ever called me.
A police department demanding I come in and turn myself in right away. It took about a minute for me/them to realize that they were given a wrong number and I wasn’t the person they were looking for.
When I was in my teens, I got a series of phone calls from someone who was clearly watching me/our house. They always called when I was alone. Sometimes they just breathed loudly. Sometimes they would tell me what I was wearing/doing.
Around this time, I felt like I was being watched in my room most nights and this turned out to be true after I heard a noise one night and my dad went out to find a still smoking cigarette butt on the ground under my window.
Nothing came of this. My parents (not the best) didn’t call the police. They just put up new curtains in my room and kinda ignored it. I never found out who was doing it and it eventually stopped.