The current case of the FAS Russia regarding the largest mobile communication operators setting different prices for telecommunication services in intranet roaming and in the home region poses the question of whether it is correct to consider such services as «one and the same product» in the antitrust definition of product markets. Antitrust methodology suggest that these services should then be close substitutes from the point of view of the consumers, which appears not to be the case. On the contrary, telecommunication services are characterized by a high degree of complementarity, including transaction complementarity on the consumer's side. In antitrust practice, in order to determine market boundaries in such situations, the cluster market approach and the bundling approach are used in addition to the narrow method of market definition. The article discusses in detail these approaches, describes the criteria for their use and justifies the applicability of these approaches to cellular communication services. It appears that using either the cluster market or the bundling approach to defining market boundaries in the case of intranet roaming has substantial basis. Taking specific components of a cellular tariff plan and treating them as a separate product market for antitrust purposes increases the risk of type I and type II enforcement errors.