Customer centricity is key to the success of modern business companies. Recently, a lot of attention has been paid on machine learning methods for customer satisfaction analysis and monitoring of trends in customer opinions and sentiments. The current study aims at predicting customer satisfaction from contact center chat services – a domain largely underrepresented in the existing literature devoted on sentiment analysis. Main goal of the current paper is to analyze chat communication between operators in a call center and clients of a large bank and develop a methodology for sentiment analysis based only on chat data. This study is the first explicitly aimed at service rating prediction based only on textual features combined with grammatical information extracted from chats. The proposed approach is purely statistical and does not rely on sentiment lexicons. Drawn are valuable conclusions regarding the usefulness of different feature sets, text normalization techniques and levels of chat data representation. Main practical benefit of analyzing customer satisfaction is that it may lead to large improvement of customer services quality, as well as better understanding of customers’ experience, pain points and needs which underlies its importance in the financial services domain and not only. The study contributes to the literature devoted on practical applications of text analytics in Bulgarian and sentiment analysis for low-resource languages. To the best of the author's knowledge, the current study is the first for this combination of task, language, and data domain. The use case under study is in the banking domain but results and findings might be helpful in any other domain in which similar communication is being analyzed.