As long as it was cancelled at least 24 hours before the trial period ends, you should have been in the clear as detailed in the Support Article where is states:
- If you signed up for a free or discounted trial subscription and you don't want to renew it, cancel it at least 24 hours before the trial ends.
If you want to cancel a subscription from Apple - Apple Support
So in that case, I would contact Apple directly and be prepared to provide any supporting documentation that may show cancel date and time and trial period time and also state that it does not show as being able to refund using the reportaproblem website.
Contact Apple for support and service - Apple Support