Do you have/use caller ID?
Will you answer the phone if the name and/or number that appear on caller ID are unfamiliar?
How do you respond when someone you've never heard of leaves you a message: 'Hello X (your name). This is Y (their name). Could you please call me back at xxx.xxxx' with no indication why they're calling, and what they wish to speak about.
I am becoming increasingly cranky/anti-social and often don't pick up the phone and don't call back.
What do you do?