Cancel pending Apple Pay charge

It is not possible to cancel a pending charge because it has already been approved by you or a user of your phone that was given the Passcode to complete the transaction. Transactions managed by Apple require you to double click the side button with the amount and terms of the transaction showing on the Approval screen, followed by authentication with Face ID/Touch ID or Passcode. For a Free Trial, there is also a message that says to avoid the subscription charge you must cancel the trial at least a day before it ends.

You can try to request a refund, but that is only possible after the transaction has been paid. In most cases all transactions in the App Store are final due to the explicit actions required to approve them, but at times Apple may provide a compassionate refund.

Request a refund for apps or content that you bought from Apple - Apple Support