Conducted a churn and billing analysis on a dataset of 20,000 French telecom subscribers (Iliad/Free) using Python. Performed cohort-based retention modeling, analyzed churn dynamics by technology (Fiber vs ADSL) and acquisition channel, and explored cumulative billing patterns over the customer lifecycle. Delivered key insights on early-tenure churn risk and long-term revenue drivers, and outlined a predictive churn scoring approach to enable proactive, data-driven retention strategies.