The arrival of the mobile telecommunications service industry and its rapid and widespread growth is the most significant developments in the fields of communication. The aim of this study is to propose a decision-making structure to determine the appropriate Global System for Mobile Communications (GSM) operator. There are varieties of driving factors involved in choosing the most suitable GSM's operator, and all these factors have positive and negative interactions with each other; in this regard, we apply an appropriate multi-criteria decision-making method. Due to the interdependency between these criteria, we use Analytic Network Process (ANP) that generalizes Analytic Hierarchical Process (AHP) by considering the interdependencies among factors. The results of this method illustrate that customer satisfaction and word of Mouth are the most important factors in selecting GSM's operators in Iran. The proposed structure provides valuable insight into the process of GSM's operator selection for GSM managers and practitioners. It can be applied as a practical assessment tool providing an evaluation of GSM operator's market share and identifies areas of weakness that negatively affect success in market share.