In this paper, we consider call center models with impatient customers. Our purpose is to study the effect of informing customers about their anticipated delays upon performances. First, we consider a single class call center model. We propose a method for modeling the customer reaction with regard to delays information. Thereafter, we conduct a numerical comparison between performance measures of both models with and without information. The experiments show how the expected customer satisfaction in the model with information would tip the scales in favor of that model. Second, we address the analysis to the case of a two-class call center with strict priority. Finally, some practical issues are discussed. In particular, we propose a method of delays announcement referred to as announcement by increments. We shown how this method would improve the system behavior through reducing errors approximations.