A telephone operator told me that one day she received a phone call. She answered, "Public Utilities Board." There was silence. She repeated, "PUB." There was still no answer. When she was going to cut off the line, she Heard a lady's voice, "Oh, so this is PUB. Sorry, I got the number from my Husband's pocket but I do not know whose number it is."
Without mutual trust, just imagine what will happen to the couple if the telephone operator answered with just "hello" instead of "PUB".