This might only work in a small town where there are just a couple of agents, but when my mother was trying to get a rental agent to manage her building, she used to leave a message for one ‘accidentally’ using the name of his competitor.
Like: “Sammy, I’d be glad to show you the building. Either tonight or tomorrow evening will work for me.” But she left this message not at the Sammy Smith Agency, but at his competitor the John Johnson Agency. That seemed to get John Johnson to call back right quick. (And he would never mention her ‘mistake’ in the message she left.)