Hold on sis, they will give up. You could answer them with a colleague name. Saying you are away and ask for their number to call back.
Thank You green72. My flat owner/friend is considering the Cctv idea. She quite scared coz usually the nanny and 2 kids are at home. I am all for it for added security as well. I also felt a little better since I told my boss about the call. He told me not to answer my desk phone line for the meantime. He is really showing some support. I am still waiting for my IO to call. I have been leaving messages but he hasn't gotten back to me yet and I don't have his handphone number.