To cancel your ChatGPT subscription, you need to do it through the same billing...

https://sierra-wiki.win/index.php/I_Canceled_ChatGPT_But_Got_Charged_Again_-_What_Are_the_Real_Causes%3F

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