How do I request a refund for Duolingo subscription?

Do you see the charge here?

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

If not, then the subscription being managed by Apple and it is with DuoLingo that will have to provide a resolution. If you do see the charge there, then it is managed by Apple and you will also want to make sure to cancel the subscription.

View or cancel app subscriptions on iPhone - Apple Support

Apple cannot work a refund for a third-party application subscription through the App Store. That is between you and the terms and conditions of Duolingo regarding their refund policy. Contact that vendor and request your refund.

DuoLingo has 2 methods for subscriptions/refunds and it depends on the method used. They offer website subscriptions that are only managed by them and in-app purchase subscriptions managed by Apple. The in-app purchase requires you to double click the side button with the amount showing on the screen, followed by verification with FaceID/TouchID or Passcode. It is not something that can be done by accident.

Many times people will start a free trial and forget to cancel it as least 24 hours before the trial period ends, then it will become a subscription, but that is true for all free trials and they have no one else to blame other then themselves.

In most cases, all transactions in the App Store are final. At times, Apple may provide a compassionate refund, but it should never be expected.

Wrong,it shows in the app of duolingo that you need to contact apple for a refund and that they cannot do anything. I have the same problem atm,payed 90€ without me wanted it. Lost my last money for this month hoping for a refund from apple. Otherwise i will be eating nothing for the rest of the month. Sadly but its no joke. Its a scam company.