Unpaid accidental subscription preventing App Store downloads

Not all apps offer a free trial to try them out first. When making a purchase on your device, it requires you to double click the side button with the amount showing on the screen and the length of the subscription you have chosen. After accepting those terms by double clicking the side button, then authentication proceeds with Face ID or Passcode. You should not have been surprised about that charge you had agreed to.

Cancelling any subscription just means it will not be renewed again at the end of the term, it does not remove the charge for the subscription.

A pending charge cannot be removed and you also cannot request a refund on a pending charge. All you could do in that case is pay the amount you agreed to and then attempt to request a refund. 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. It just should never be expected though.

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

And finally, you are not speaking to Apple here as this is a Community forum of other users just like you. If you would like to speak to Apple directly, that is done here:

Contact Apple Support - Apple Support

This is a user-to-user technical Support community. You aren’t addressing Apple. We can’t do anything with your account.

Try contacting Apple support directly: Contact - Official Apple Support