A call center in a company is a centralized office that answers incoming telephone calls from customers or makes outgoing telephone calls to customers. A call center may also provide fax, Voice over IP (VoIP), e-mail or web-based interactions. This paper proposes a plug-in modular architecture for an Internet call center with waiting time prediction. We implement this plug-in module in the SIP Express Router (SER) platform. Then we propose two output measures and develop a discrete event simulation model to investigate the performance of the waiting time prediction algorithm for the call center. Our study indicates that the waiting times can be more accurately predicted when the call arrival rate is large.