This paper describes how simulation was used for business case benefits and return on investment (ROI) projection for the procurement and rollout of a new call routing technology to 25 call centers. With investment costs of about 17 million dollars and annual operating costs of about 8 million for the new technology, we needed to determine if the technology would provide enough cost savings and cost avoidance (through reduced trunk costs, increased agent productivity, and ability to service more calls) to warrant its nationwide implementation. We constructed a model of the existing call center environment consisting of 25 call centers where calls were distributed to the sites based on a system of percentage allocation routing; for example, the telephone network provider directs calls to each site based on the number of agents scheduled. We then modeled the same call system dynamics and intricacies under the new call routing system where calls are distributed based on longest available agent. Subsequently, we conducted average day simulations with light and heavy volumes and other “what if” laboratory analyses and experiments to facilitate planning decisions required to be documented and substantiated in the business case.