Mobile number portability (MNP) policy highlights the problem ofsubscriber churn and thus enhance the liquidity and competition of the telecommunication market. China will implement MNP policy on November $1^{\mathrm{s}\mathrm{t}}$, 2019 after 9 years of trials. This paper timely proposes, validates, and productizes a game theory assisted machine learning scheme to help the mobile network operator (MNO) in China make a strategy to proactively cope with their competitors in the same MNP market. The scheme further develops a set of MNP tactics for the MNO to detect user churn behaviors and to remedy the users with appropriate treatments. Experimental results demonstrate that the scheme can guide the MNOs to make targeted MNP strategy and precisely identify the “abnormal” subscribers who tend to churn out and potential new subscribers who may churn in. The scheme has been successfully implemented in production to greatly improve the marketing efficiency and user satisfaction in terms of an approximately 50% reduction of user churn for a tier-1 MNO in China.