Hello, 

Go to the police station and lodge a FIR against him or before lodging the FIR you may send a legal notice to him through an advocate. 

regards 

Dear Client,

Any man who follows a woman and contacts, or attempts to contact such woman to foster personal interaction repeatedly despite a clear indication of disinterest by such woman - is a criminal offense, he won`t even get bail. Complain to police, they will let him understand nicely and still he repeats than lodge FIR.

You can even complain online.

Approach the cyber cell of Mumbai Police and report this case to them by way moving a detailed complaint.

In your complaint, incorporate all relevant information and annex the relevant screenshots. 

record his calls 

2) file police complaint against guy under section 504 , 506 of IPC 

3) enclose copy of messages received by you 

file a police complaint against the said guy for causing mental harassment to you,

1. Record all his messages and request him by sending mail  not to send any further mail to you.

2. If he still continues to mail you, lodge a police complaint against him alleging that he is harassing you despite repeated requests not to send you mails.

You may either block him from all social media network and dont entertain a call from any unknown number in future or better make a complaint with the local or cyber crime police about this.