Uhm....i have seen this topic but never read it and now my curiosity killed me :D
Anyway i have read many comments and i like to give my thought....
First at all....parents.....are geneticaly idiots...they dont notice the problem until the end.....then dont count really of them...you have to make the first moves alone....
Police.....useless because you are young and surely thinking that you are little paranoic
Then you have to try to solve the problem alone (at first)
And now the hints
- dont show your fear, you will make his/her game, when you receive the phone calls just follow them with some irony..this will confuse the culcript
- think seriously who can do this kind of "jokes" if a friend, an ex boy friend or maybe a girl with envy problems. Why that? Because if the culcprit phone you he know you and i dont think that you spread your personal details around internet (pics apart) then he is close to you or your friend....and the fact that he dont talk but make simply dirty rumors is a little evidence that maybe you can identify him
- when you will find him / her then.....at your choice but never lower oneself at his level
- I hope that him/her is not an MT user too :D
Anyway the very most important thing is not showing fear....your fear is him/her food, hope to be useful :D