The integration of Generative AI (GenAI) chatbots in education is transforming personalized learning, yet their effectiveness in online distance learning remains underexplored. This study investigates how a GenAI chatbot tutor facilitates personalized learning in an online higher education setting, using the Community of Inquiry (CoI) framework. A qualitative case study approach was adopted, analyzing chat logs, chatbot platform analytics, and a semi-structured interview. The study included four voluntary participants who engaged with the chatbot as a learning support tool, while one participant was interviewed to provide deeper insights. Findings indicate that the chatbot contributed to cognitive presence by scaffolding inquiry and promoting adaptive knowledge construction, social presence by enhancing engagement and fostering an inclusive learning space, and teaching presence through context-aware responses and real-time learning insights. However, technological constraints, inconsistent response accuracy, and limited handling of complex queries were identified as challenges. These results suggest that while GenAI chatbots enhance personalized learning, they should be integrated as supplementary tools rather than standalone tutors. Ethical considerations, including data privacy, transparency, and AI reliability, must also be addressed. Future research should focus on refining AI-generated responses, investigating long-term learning outcomes, and optimizing human-AI collaboration in education.