We consider an inbound call center with a fixed reward per call and communication and agent costs. By controlling the number of lines and the number of agents, we can maximize the profit. Abandonments are included in our performance model. Monotonicity results for the maximization problem are obtained, which lead to an efficient optimization procedure. We give a counterexample to the concavity in the number of agents, which is equivalent to saying that the law of diminishing returns does not hold. Numerical results are given. Subject classifications: call centers; monotonicity. Area of review: Manufacturing, Service, and Supply Chain Operations. History: Received July 2008; revisions received January 2009, August 2009; accepted October 2009. © 2011 INFORMS.