Paper presents a system dynamics approach for modeling mobile service competitive market of the region and forecasting market development. The model includes dynamic competition between operators. The pricing policy, service quality, subscriber base, potential subscribers, marketing, etc influence their number of subscribers. The task of defining the market share carrying capacity to forecast the sales process is described. The method for the saturation level identification is considered and the problem of the optimal pricing is formulated. Real data from several regions of Russia are used in this paper.