I have been doing a lot of phone calling lately. This has been to Sam and Sally Public mostly. It surprises me how poorly people answer the phone. Answering the phone with a short "hello" in a tone of suspicion is not the way one should start a conversation. Instead, say "hello, this is so and so speaking". Have a brightness to your words and smile through the phone. Answer the call with gladness that someone has taken an interest in you. Welcome the conversation and put the shields down.
If you don't have time to take a phone call, don't answer the phone. It doesn't make any sense that people picked up the phone only to say they don't have time to talk. If you don't have time to talk, let the phone ring and let it go to voice mail.
Set up your answering machine message properly. State your name and ask callers to leave their name, phone number, and message. Anyone can do this. The outgoing message helps to confirm that the caller dialed the right number.
People need to get better at their phone speaking skills. With a little effort, I think they can do it.