Infomercial call centers answer calls in an order that reduces the number of abandoned calls to minimize lost revenue. We study a multi-class queuing system with a single server and customer abandonment, motivated by the case of infomercial call centers. We fully characterize the structure of the server’s optimal scheduling policy that minimizes the long-run average customer abandonment cost. We show that the optimal service policy is a static priority policy. We derive sufficient conditions under which the so-called b μ –rule is optimal. Under the b μ –rule, it is optimal to give priority to the customer type that has a higher service rate ( μ ) and higher abandonment cost (b), i.e., higher index b μ . We numerically test the robustness of our proposed policy in more general settings, including multi-server infomercial call centers.