Voice services were the main source of revenue for French fixed and mobile telecommunications operators in the early 2000s. This situation has progressively changed. Nowadays broadband services are the main source of revenues for fixed line operators and the same phenomenon is taking place in the mobile sector. As operators launch new services, they maintain the existing ones in their commercial plans, while allowing consumers an unlimited usage of the feature for no extra charge. We refer to this trend as commoditization. In order to explain the rationale behind this phenomenon, we will study the causes and effects of fixed and mobile voice services commoditization on the various operators by examining the links between market structure, regulatory decisions and operators' corporate strategies. Our goal is to determine to what level commoditization process is the result of operators' corporate strategies, and to assess the role played by regulatory decisions in the process.