A decade ago, most companies hadn't even considered the revenue potential of inbound customer service call centers. But today, call centers generate up to 25 percent of total new revenues for some credit card companies and up to 60 percent for some telecos. The top priority of agents in these call centers is resolving service issues. But they are also encouraged to initiate conversations to uncover the needs of customers, and this component of the job can lead to sales of new products or upgrades of current ones.

Partly for fear that a sales pitch will put off customers seeking service, other sectors, such as retail banking, have been slow to turn service calls into sales calls. Yet our research indicates that when agents meet the service needs of customers and then ask them about their broad needs in a sincere way, customers are receptive to buying new products.

We also find that companies have failed to tap the full revenue potential of their call centers because they just don't understand the extent of the opportunity. In retail banking, for example, we estimate that every five inbound service agents could generate as much new retail business as one mature branch....