Yes.
All trial service, at the end of the trial period, customers must self cancel the service should the customer not want to continue with the service. Otherwise, Singtel will bill you the regular price of the service in your monthly billing, subject to pro-ratings for the month, once the trial period has lapsed.
During the free trial, there will be no charges incurred. Charges will be incurred, based on pro-rating, once the trial period has lapsed and customer did not call in via hotline to terminate or self terminate using Singtel app.