Duolingo's Free Trial Turns into Costly Subscription

I decided to give Duolingo a try by signing up for their two-week free trial. They assured me that I would receive an email notification a few days prior to the trial's end, giving me the option to cancel the subscription if I wished. Unfortunately, that email never arrived, and now I find myself charged a staggering 330 TL at the end of the trial period. Despite my immediate request for cancellation, my refund is still pending. What's worse, the membership status indicates that it will expire a whole year from now. I strongly demand a full refund for the unauthorized charge and seek your assistance in promptly resolving this matter.