If your school offers subscriptions, users may have the opportunity to explore the service with a trial period before committing.
In this article, we will explore how to prolong a user's trial subscription using Stripe.
Extend Trial period
1. Ιn your Stripe dashboard, navigate to Payments → Subscriptions, and click on a specific customer.
2. Click on Update subscription under the Actions button.
3. On the customer's account page, scroll down on the Free trial days and customize the remaining days. 
4. Click on Update subscription.
Change Billing Cycle
This procedure can also serve to adjust the billing cycle of a subscription. For instance, if you desire to shift the subscription renewal date from, say, the 10th of a month to the 20th, you should initiate a Trial period for the user. Following the conclusion of the Trial period, the user will transition into a subscribed status, with the updated billing date in effect.
Prorate should be disabled to avoid giving credits to a user after turning the user's subscription to Trial (when a customer’s plan changes during a billing cycle, a proration line item is applied on their next invoice. They receive a credit for the unused portion of the old plan and are billed for only the remainder of the month for the new plan). You can find more information here.