Mental harrasment and continous insulting messages

I was in a relationship with a boy for two months. We separated after that because he confessed that he already had another girlfriend. But that guy has sent me some really insulting messages falsely accusing me of creating problems between him and that other girl, and he also accused me that I am pursuading his other girlfriend not to be with him. He abused me on text message and twi days later abused me on phone call. He even called me a slut (as told to me by his other girlfriend) He even abetted his other girlfriend by lying about my character ,to threaten me and insult me and she did accordingly. He also threatened me that if I filed a complain then he will inform everything to my parents. I am very much depressed since a month because of all these messages and blame games. I have all the messages saved with me but no call recorded. Where shall I file a complain, ncw or police? please guide me. Will I be provided with public prosecutor? Will I need to attend all the court proceedings?