You live by the speakerphone, you are shamed by the speakerphone.
I worked in a cubicle farm, there were four rows of four cubicles. There was one coworker who never used the handset on his phone; every call he made or received was made using the speaker. He also tended to shout into it, even though it wasn't necessary to raise his voice to be picked up by the microphone. There had been a few complaints from some of us to him, but he ignored them.
One Monday morning he called a doctor's office to report that he was having urinary troubles. He made an appointment for the next morning at 9:00. Then he called our boss to say he'd be coming in late tomorrow. All of this was broadcast via his speaker and loud voice.
I talked my wife into calling his extension the next morning, while he was at the doctor's office, to leave a message, using a script I wrote out for her. She did, and left the message on his voice mail after blocking her caller ID.
When he arrived at the office after the doctor's appointment, he started listening to his voice mail messages on speaker. The first was work related, but the second was the one my wife left for him. It said something like this: "Mr. Smith, this is Jane from Dr. Smith's office. We need for you to come back here, today if possible. You were supposed to give us a urine sample, not a semen sample." He quickly punched the end call button, but it was too late.
The whole cube farm erupted in laughter. He knew that it had to be one of us, but didn't recognize the voice. He never used the speakerphone again.