Was this a trial period that you failed to cancel at least 24 hours before the subscription start date? In that case, if the transaction is pending for the subscription due to a payment issue, then that will need to be paid. There is no way to cancel a Pending charge and it will not appear in your Subscriptions now to cancel until that subscription has been paid.
You also will not be able to continue to use the App Store, while you have a Pending charge until you have paid the amount you owe. In order to agree to the terms of the free trial, you must double click the side button where you see the trial period, subscription price, subscription start date and the VERY important message that says to avoid the subscription charge you should cancel a day before the start date. After you explicitly agree to those terms, then authorization proceeds with Face ID/Touch ID or Passcode.