calls frequently with no answer and call back always busy

phone call from North Carolina with this phone number, no one on line when answered. Called back busy. Used speed dial to keep calling and eventually intercepted what sounded like automatic dialer dialing out.

Keep calling, wont leave voicemail or answer when I return.

PLEASE stop!!

This is a NC State University number. The calls are probably regarding graduation, alumni matters, or messages from the student body president. Indeed it doesn't leave a voicemail, and it is an automated message machine. No big deal. If you're not from NC State then call the university and ask them to remove your number, clearly someone with your number in the past was a student or alum of NCSU.