Update next_billing_date in Rails App with Braintree

Hi, I recently developed a Rails app using Braintree Recurring, when the user subscribes, the information such as plan_name, next_billing_date ware saved into the database. However, I found the next_billing_date was not update if the current billing period was finished and the latest next_billing_date was changed. How do I retrieve the next_billing_date from Braintree and update in my database automatically?