A free trial may have expired, but like any free trial it automatically becomes a subscription unless you have taken steps to cancel the subscription at least 24 hours before the trial period ends. Apple has no idea you also signed up on the developers website. The only one that would know you have 2 subscriptions is the developer for the service you are using.
You can try the link provided to request a refund, but in most cases all transactions in the App Store are final. Apple may provide a compassionate refund, but it should never be expected. You may have a better chance at getting a refund from the OpenAI website, as they were aware that you already were paying for a subscription with them. After that cancel the subscription with Apple and when that subscription period ends, then sign up at the OpenAI website if that is who you want to manage the subscription.