Consultants recommend picking a building or design that has your call center on one floor. This lets you orchestrate layout and supervision more easily, as opposed to having people run among different floors. Plus, multi-story buildings often have very little parking and tend to be more expensive. This setup lets you take advantage of economies of scale provided by the building and site. Downtown areas with multi-story buildings tend to not work well for many call centers.
Real estate is usually more expensive and parking is limited and costly.
But these locations provide excellent transit service and amenities. In many cities there are warehouses that offer large open spaces suitable for call centers.