This is a very serious (although relatively rare) issue. Stalking (in person or by telephone) is unlawful in North Carolina. See N.C.G.S. § 14-277.3 (stalking) and N.C.G.S. § 14-196 (harassing phone calls).
If you reasonably believe the student, faculty or staffmember is engaging in conduct unlawful under the statutes, and the person does not desist after being asked to do so, report the conduct to your Department Chair and to the campus police.
Statutes outlining stalking and phone harassment (PDF, 58 KB)