How do I cancel an accidental subscription and unblock my Apple Account?

I am doing some interpolating here and thinking the subscription has charged you and until you pay for it Apple will not let you do additional downloading.

Click on this link to review the information in the support article about canceling subscriptions ➔ Cancel a subscription from Apple - Apple Support

• “If you signed up for a free or discounted trial subscription and you don't want to renew it, cancel it at least 24 hours before the trial ends." By using an app like this you are automatically agreeing (always read the fine print) to this happening, are responsible for reading if this will happen, and canceling the subscription before the trial ends. E.g., Bait and switch on Apple apps - Apple Community Exceptions apply in some countries ➔ About canceling subscriptions in Germany, Israel, South Africa, or Türkiye - Apple Support

• Deleting an app does not cancel a subscription.

• Canceling a subscription does not automatically start a refund.

• This thread (particularly posts by Mac Jim ID) outlines complex scenarios regarding subscriptions and trials. ➔ Refund request for unintended Snapchat Pl… - Apple Community

You may have canceled too late. In that case you will have to pay what is owed and then try for a refund. If you wish to pursue a refund, follow the directions in this support article about how to request a refund for apps or content that you bought from Apple ➔ Request a refund for apps or content that you bought from Apple - Apple Support The likelihood of you getting a refund may vary greatly from region to region as provided in section B of Legal - Apple Media Services - Apple . Typically refunds are entirely discretionary and not guaranteed. Special terms may apply for some countries: About canceling subscriptions in Germany, Israel, South Africa, or Türkiye - Apple Support

Read this support article for information about how long it takes to receive a refund (if one is granted), and how to check the status of a refund for apps or content that you bought from Apple --> Check the status of a refund for apps or content that you bought from Apple - Apple Support

● Store credit—It might take up to 48 hours to see the refund in your Apple Account balance.

● Mobile phone billing—It might take up to 60 days for the statement to show the refund. Processing time might be affected by your carrier. You can contact your carrier for an update.

● Credit and debit cards, Apple Pay, Apple Cash, and all other payment methods—It might take up to 30 days for the statement to show the refund. If you don't see the refund after 30 days, contact your financial institution."

Not sure what you mean by an accidental subscription.

In order to start any Free Trial/Subscription you must double click the side button on the Approval Screen where you would see the Free Trial length, Subscription Price, Subscription Start Date, and the very important message that says to avoid a charge from the free trial you should cancel at least a day(24 hours) before the subscription start date. If you agree to those terms by double clicking the side button, then authentication proceeds with Face ID or Passcode.

Those would be the terms of the transactions that you agreed to and if you forget to cancel the free trial in that time frame, then you owe the amount for that subscription just like you had agreed to pay. While you owe money you will not be able to use the App Store for any reason. Is that what you mean by an accidental subscription?

In most cases all transactions in the App Store are final, but at times Apple may provide a compassionate refund. It should never be expected though. If your charge is showing as Pending, it is not possible to request a refund and you would need to first pay for that amount you owe, then you can request a refund.

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

If that is what happened to you, I would recommend that when using a Free Trial to create a reminder to cancel that trial to avoid the subscription charge. It is as easy as saying "Hey Siri, remind me on xx/xx/xx to review my free trial and cancel if necessary".