Public sector banks continue to be the main providers of banking services to households, businesses and farmers in Karnataka, a state that gave birth to several of India's leading banks. The consolidation of public sector banks between 2017 and 2020, which reduced their number from 27 to 12, brought major changes in branch operations, loan processing and technology-based services. While earlier studies have examined bank service quality in general, few have compared how different categories of customers experience problems with public sector banks. The present study therefore examines the problems faced by four categories of customers of public sector banks in Karnataka, namely borrowers, official (salaried) customers, business customers and agriculturists, and tests whether their level of perception differs significantly. Primary data were collected through a structured questionnaire measured on a five-point Likert scale, covering problems related to account opening, attitude of bank officials, waiting time, guidance, technology and security, service charges, timely support and group-specific loan and account issues. Mean, standard deviation and ranking were used to identify the major problems, and one-way Analysis of Variance (ANOVA) followed by the Tukey HSD post-hoc test was used to compare the groups. The results show that business customers perceive the problems most strongly (mean = 3.89), followed by agriculturists (3.75) and official customers (3.74), all of whom fall in the agree range, while borrowers remain largely neutral on general service issues (3.30) but strongly agree that loan procedures are lengthy. Long waiting hours, unfavourable attitude of officials, repeated visits, lack of timely support and unnecessary charges emerged as the most serious problems. The ANOVA result (F = 32.89, p < .001) confirms a significant difference in perception among the four groups, mainly between borrowers and the other three groups. The study suggests group-specific measures to improve customer satisfaction.