Just another point of view; many times HR will call X amount of prespective employees. Some will not pass the phone interview, some will not want the job, some, like in this case, will not answer and be passed over until the next round of calls go out, and finally, some will actually be called in for the interview. It is all based on numbers. If you need to hire 10 pilots, 50 calls go out.
If you are truely interested, stay on their radar. Just be careful not to be annoying.