If you do not see the charge when requesting a refund, then the Free Trial was started on their website. This is very common when you find out about the app from a Social Media link or Website advertisement. Those will direct you to their website to start the free trial and bypasses Apple's ability to cancel/refund the charges. For any trial started from their website, you will need to request a refund from them and also cancel the subscription on that same website.
If the Free Trial was started in the app after you downloaded it, then you will see it in the provided link to request a refund. Also make sure you cancel the subscriptions that has now started. Whenever you use a Free Trial it will always convert to a subscription unless you cancel at least 24 hours before the trial period ends. It makes no difference if you use the app or not.
If you want to cancel a subscription from Apple - Apple Support