I'm trying to get hold of someone in the office..

The Exec Officer works Monday-Wednesday, 9am-4pm - but she also has to attend meetings, careers events, photocopy... so the fact that she's working doesn't guarantee she'll be in the office or near the phone! Your best bet is to either email or to ensure you ring during office hours and keeping ringing until you get through. Try emailing at any time as she does check email outside these hours in case of emergencies.