To cancel your ChatGPT subscription, you need to do so through the same channel...

https://garrettwigp625.tearosediner.net/what-does-manage-on-the-app-store-mean-in-chatgpt-settings

To cancel your ChatGPT subscription, you need to do so through the same channel you used to subscribe—whether that’s the web via Stripe, Apple, Google Play, Business, or API