I had to get a restraining order against someone due to abuse/harassment, and I second much of what other posters have said. From my experience, and from what I know of the general process:

You have already made it clear to FOO that you are not interested in being contacted. You have taken steps to remain insulated from their harassment, but they have persisted in their attempts to contact you.

This is criminal behavior. It's harassment.

Contact your local PD via non-emergency means- even just by walking into the station- and they will be able to help you. The police are often able to generate a temporary order; you will then go before a judge, who will have the power to grant you a permanent restraining order that specifies no contact. This means via phone, email, mail, third party- no contact means NONE. They will also be ordered to stay away from you and places that you frequent.

They face jail time if they violate it. It's serious stuff, but very effective. This order will be served by the authorities in the area where they live (often the sheriff's department). Mine was in the same state, but handled between two different counties.

I suggest the following documentation: 1) Statement letter. Keep it clear and concise; just the facts. 2) Timeline of events. Give a general idea of how long this has been happening, when you requested that FOO cease and desist; etc. 3) Printouts and screenshots of emails/texts. A CD of relevant voicemails wouldn't hurt either. It's all evidence and will weigh in your favor. 4) Information such as the street address of FOO, for service purposes. Your address can be hidden at your request.

I breathed a sigh of relief when I had my order in my hands. Sure, it's a piece of paper- but that paper can put them behind bars. They will be forced to take it seriously.

I'm sorry they haven't respected you and your wishes for NC- this might be your best bet to make it happen.

Best of luck, OP.