If you ask me whether this move is annoying, i would say 'YES' 50 times over, but apparently it works like clockwork. One candidate call this company's HR department one time for 2.5 weeks until he got an interview with the company. First he would talk to the representative there, then he would leave voicemail. So this is the reward for being persistent. You don't have to go that extreme, but you can use that to your advantage.