Netshort Charged Me Twice for a One-Week Subscription

I downloaded an app called Netshort through the Google Play Store on September 29 for a one-week trial and paid 398 TL for the app's one-week plan. However, despite no subscription appearing under my subscriptions, an additional 398 TL was charged to my account.

Since my subscription does not appear in the system, I cannot follow the standard cancellation steps through the Google Play Store. I also cannot find any option within the app to terminate the subscription. Despite contacting customer service, I have not received any response.

I demand an explanation for why I was charged when no active subscription is shown for the app, a prompt refund of the additional 398 TL, and the immediate cancellation of any Netshort subscriptions that may be linked to my account.