Some phones have an option called a rejection list. It would be under call settings if you have this option. You would simply add the number to the rejection list and the call wouldn't go through. Actually the caller just goes straight to voice mail.
If you do not have the rejection list, then assign a silent ringtone to the person. That way the person calls, you won't hear them calling. You can just ignore the call.
You also tell the person that every call is now being forward to the police. That should hopefully scare them and then they would stop!
You can block up to 5 numbers from calling or texting you for free at http://www.vzw.com/spamcontrols
or go to My Verizon > My Services > Verizon Safeguards > Spam Controls > Call & Message Blocking
There you will enter in any 5 numbers you wish and they can no longer call you on any device.
You will need to set up Call & Message blocking. This will allow you to block up to 5 numbers from calling/texing you. You must sign in as the account holder online, then select my services tab then Verizon safeguards tab on the left side of the page. Next, click Spam Controls. Add up to 5 numbers and click save. Block will expire in 90 days;however, you can sign back in to add a block again if necessary.