The conducted study focused on a multinational ITC (Information Technology and Communications) company. Empirical research aimed to evaluate organizational culture based on Denison’s model through four features: capacity development, basic values, customer orientation, and goals and objectives. At the same time, the study analyzed service provided to customers, taking into account its three phases: pre-transaction, transaction, and post-transaction. As research methods, we used a questionnaire-based survey and direct observation. The results of the study demonstrate that the company has a strong culture based on an adequate core value system (shared by company members), innovative and effective human capital management practices, and customer orientation. All characteristics ensure the integration of sustainability principles into strategies, policies, and management practices of the company. At the same time, the authors develop a design and analysis model of the impact of organizational culture features on customer service effectiveness, highlighting that the four organizational culture features are good predictors for improving customer service effectiveness, which promotes an ethical business model and sustainable pursuit of economic, social and environmental performance. The study identified a set of good management practices and solutions in the design, operationalization, and monitoring of customer service.