The main purpose of this article is to explore how standardization of the public service provision and introduction of customer service standards affect the de facto discretion of civil servants. The study uses a qualitative case study approach. Two main research methods were used to gather data – semi-structured interview and document analysis. Analysis of the empirical data revealed that written standards only partially affect the de facto discretion of civil servants. The customer interaction standards define only a few civil servants’ actions, and do not cover all aspects of the communication between civil servants and customers. Application of written standards is flexible especially in non-typical situations. Customer service standards do not restrict the actions of civil servants when they focus on customer problems, which is especially important when dealing with socially vulnerable customers. This study explores the use of customer service standards as a public management tool. The research data can be useful for understanding and improving customer interaction standards and its practical application.