are they a "real life" or "on line" person?
Either way, first and foremost you need to tell them you no longer wish to have any communication with them and if they continue down this path, you will look into necessary actions as needed- block all means of communication with them; block emails, block their telephone number by calling the phone company, block their cell phone number, etc. Keep records with dates and times, and photos/print outs if necessary to back up your story for the future if it need come to that. If that doesnt work and they get around it by using other peoples phones or getting different email addresses - then change YOUR phone number and email address, explaining to the phone company why you've had to change it. Many times they'll waive the fee if you're being harrassed. If they continue to harrass you - tell them
one time and one time only that you will call the authorities on them, end of discussion. Will it tick them off? Probably - but... are they ticking you off and upsetting you? Yes. Is it worth it to your well being? Absolutely Not.
You said you've tried to walk away and do the right thing - they wont let you and keep finding you. You have the control here - if you keep handing it over to them, they know they have the control over you sweetie.
Hard to do, but sometimes so very necessary for our own well being.
Hang in there... I'm praying for you.