This document discusses churn management in mobile communications. It defines churn as customer attrition or loss and churn rate as the number of customers who discontinue service divided by the total number of customers. It identifies reasons for churn such as easy switching between providers and inadequate services. It discusses types of churn, data transformation for modeling, identifying customers' propensity to churn, and calculating customer profitability. Finally, it outlines strategies for reducing churn such as identifying valuable customers and developing win-back policies.