Exclude Existing Subscribers from Free Trial

What I would like is that, for all future subscriptions, any customer who has already purchased or subscribed in the past should not receive the 7-day free trial even when they had subscribe and save plans without free trials before. Only customers who have never previously subscribed to the service should be eligible for the free trial. Returning customers who cancel and later reactivate their subscription should be charged immediately without receiving another free trial period. ​