Firms are acquiring information systems capable of processing increasingly individualized demands, and are trying to adjust their production of goods or services accordingly, with more and more rapidity. The main characteristic of call centres is the direct link (via telephone) between customers and the employees of these firms. The example of two France Telecom call centres is explored here by showing the challenges facing these new activities. What incentive systems need to be set up here for workers? How can "value for the customer" (service quality) be reconciled with value for the firm (profitability)? What trade-off can be made between long-term objectives (developing customer loyalty) and short-term ones (increasing turnover)? The author shows that in the absence of real evaluation of their work, teleoperators, who deal with people whose problems arise randomly, are caught in strong and contradictory constraints.