Some operators are good and will organise something whether it is an interview or tell you to send 'em an email. Others on the other hand will completely disregard you over the phone (either receptionists who want to get you off the phone or other pilots who couldn't care less about you). but always ask to speak to the CP or GM when making a call. This method does work but prob not as much as walk-ins.
If you want advice, I'd walk in off the street well dressed with resume in hand. If the CFI or CP or even GM is out or working, then politely ask to make an appointment. This I have found usually yields the best results.
HR