Did you cancel the subscription at least a day (24 hours) before the renewal date. When you start a subscription, there is a message on the Approval Screen that requires you to double click the side button that says to avoid the renewal charge you should cancel a day before. You agree to those terms by double clicking the side button, followed by authentication with Face ID/Touch ID or Passcode.
A Pending subscription that is not paid cannot be removed because that charge was already approved and agreed to using the method described above. All you can do is pay the amount you owe and try requesting a refund. In most cases, all transactions are final, but at times Apple may provide a compassionate refund. It should not be expected though.
Request a refund for apps or content that you bought from Apple - Apple Support
I should note that you are not speaking to Apple here as this is a Community forum of other Apple users. Apple does not provide support on this Community site and they won't even see your post. If you would like to speak to Apple directly, you can do that here:
Contact Apple Support - Apple Support