Duolingo Charged Me After a Free Trial Without Clear Notice

I saw an offer for a one-week free trial subscription in the Duolingo app on my iPhone and accepted it because I understood it to be free. My free trial ended on September 8, but I did not see a clear warning that it would automatically convert to a paid subscription, and I do not remember giving any additional authorization.

After the trial ended, I noticed in my bank transactions that Apple.com had charged my card 1,200. I did not receive any notification about the charge, and since I had not specifically authorized this payment, I feel that I have been unfairly charged.

After the charge was made, I canceled the subscription myself and returned my account to the free version. However, my refund requests through both Duolingo and Apple have not resulted in a resolution, and the 1,200 charged to me has not been refunded.

I request that the 1,200 payment, which I believe was made without my knowledge or explicit authorization, be canceled and refunded to my account. I also request that users receive much clearer information about the transition from free trials to paid subscriptions to prevent similar situations in the future.