No advertised free trial period, billed immediately

I installed an application from App Store that had a 7 day free trial period and selected a yearly subscription plan after the free trial period expires. However, there was no trial period, I got billed immediately after installing the application. My request for a refund at https://reportaproblem.apple.com/ "does not meet the conditions" regardless of what I type in the description field.

I have not made any refund claims before, I have an email from the application developer that I should request a refund from Apple but I do not know how to do this.

How should I go about doing this?

The purchase was made 2 days ago and I would like to address this before the advertised free trial expires.

Thank you.