We investigate the benefits of migrating from a call center where all agents are pooled and customers are treated indifferently by any agent, towards a call center where customers are grouped into clusters with dedicated teams of agents. Each cluster is referred to as a portfolio. Customers of the same portfolio are always served by an agent of the corresponding team. There is no specialization involved in this organization in the sense that all customer portfolios as well as all agent teams have (statistically) identical behaviors. The reason for moving to this organization is that dealing with teams of limited size allows a much better workforce management compared to the situation usually encountered in large call centers. The purpose of this paper is to examine how the benefits of moving to this new organization can outweigh its drawback. The drawback comes from the fact that there is less pooling effect in the new organization than in the original one. The benefit comes from the better human resource management that results in a higher efficiency of the agents, both in terms of speed and in terms of the quality of the answer they provide to customers. Our analysis is supported by the use of some simple queueing models and provides some interesting insights. In particular, it appears that for some reasonable ranges of parameters, the new organization is attractive in the sense that it can outperform the original organization. We then extend the analysis to the case where in addition to the identified customer portfolios, there is an additional flow of calls called out-portfolio flow. It is shown that this feature makes the new organization even more efficient.