My dad was the greatest with sales calls at his business back in the day. They'd call and ask for him, he's find out who it was and ask them to hold on for a minute. Then he'd set the phone down on his desk and walk back out to the shop floor and go about working on whatever it was he was doing for about 20 minutes or so, then come back and pick up the phone and ask if the person was still waiting on the line. If they were, he'd ask them to hold on for another minute, set the phone down and walk away again.
Usually by the second time they got the hint. It was amazing how many people actually fell for this.