Answers to your questions:
Yes. Service of subpoena via telephone is legal in your case. See NCGS 1A-45(b)(1). “Service of a subpoena for the attendance of a witness only may also be made by telephone communication with the person named therein only by a sheriff, the sheriff’s designee who is not less than 18 years of age and is not a party, or a coroner.”
You do so at your own peril. See NCGS 1A-45(e)(1). “Failure by any person without adequate excuse to obey a subpoena served upon the person may be deemed a contempt of court.”
Note that Chapter 1A of the North Carolina General Statutes (NCGS) is also known as the “North Carolina Rules of Civil Procedure.”
If you object to attending the hearing, you need to follow the procedures described in NCGS 1A-45, “Subpoena.” Otherwise you will likely incur the wrath of the court that is expecting your attendance. In general, it is not a good idea to get a judge angry at you.