Abstract: This study used control charts of variables and attributes, and capability indices to analyse services quality during the period of 2004 to 2022. The control charts (-Chart and P-Chart) show that the quality is under control for the third (most recent) stage. The capability analysis of service quality for normally distributed response time using Cp and Cpk indices shows result that the process is capable. Moreover, the goodness of fit test conducted for non-normally distributed unsuccessful call rate indicates that data fit for 2-parameter exponential distribution. The capability index Ppk on unsuccessful call rates indicates that the quality process is capable. The study strengthens the general application of statistical quality control tools in monitoring and improvement of service quality. In particular, the methodology used can be a tool for telecommunication sector to timely intervene to verify achievement of their intended performance indicators. Keywords: Statistical Quality Control, Control Charts, Quality of Services, Quality Improvement JEL Classification Number: C10, C20, C30, C40