Cannot Cancel Bright Learn Fast Subscription

I have a monthly subscription to the Bright Learn Fast app, and on 28 March I was automatically charged 28 USD from my bank card. I no longer have time to use this service and the content is not relevant to me, so I want to stop this subscription and avoid any further charges. I have thoroughly checked the app and could not find any clear option to cancel the subscription. There is also no cancellation option shown under my subscriptions in the Apple Store and I have not received any email with information on how to cancel. Because of this, I feel trapped in a subscription I no longer want and do not use. I kindly request that my Bright Learn Fast monthly subscription be cancelled immediately and that no further payments be taken from my card. If possible, I also request a refund of the 28 USD charged on 28 March, since I do not intend to continue using the service.