Refund clarification for cancelled Adobe Acrobat Pro subscription

I would like to ask for clarification regarding a charge on my Adobe Acrobat Pro subscription.

I initially signed up for the 7-day free trial and unfortunately forgot to cancel before the trial ended. As a result, my payment method was automatically charged for the following billing period.

As soon as I noticed the charge notification, I cancelled the subscription immediately. At this point, I no longer have access to the premium features, and my account has been switched to the Free plan.

However, the amount that was charged has not been refunded. I would like to kindly ask whether I am eligible for a refund for this charge.

If a refund is not possible, I would like to understand why I no longer have access to the premium features, despite having been charged for the next billing period.