To cancel your ChatGPT subscription, be sure to do it through the same channel...

https://fast-wiki.win/index.php/Is_There_a_Cancel_Button_for_ChatGPT_Inside_the_iOS_App%3F

To cancel your ChatGPT subscription, be sure to do it through the same channel you used to sign up—whether that’s the web (Stripe), Apple, Google Play, Business, or API