The problem with the suggestion to dispute this through your financial institution is that the purchase was valid, if really only a misunderstanding (not reading the fine print when clicking to agree to the trial terms). Financial institutions resolve purchase issues where fraud is involved and they will probably do it by canceling your card. You are then left not only with having to get a new card but also being in Apple's bad books on a payment default which may result in a purchasing block being placed on your account until you resolve this to Apple's satisfaction.
Frankly this is a case where a mistake has been made. Apple has in the past recognized this kind of thing and issued refunds, but they are by no means obligated to do so.* From what others have described, an initial refund request may be denied by an automated system. You then have a second chance to plead your case. After it has been denied a second time then it is unlikely to receive further consideration.
You are welcome to contact Apple again. Make sure you speak with a real person. I suspect though, this may be a case of "lesson learned". :-(
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In this support article —> Request a refund for apps or content that you bought from Apple - Apple Support Apple usually says, “Some purchases from the App Store, iTunes Store, Apple Books, or other Apple services might be eligible for a refund.” It says “might” but that also implies some might not be eligible. Apple does not detail its criteria for refusing refunds. Refund terms vary greatly according to country so I strongly suggest that you check them for where you live by clicking on this link Legal - Apple Media Services - Apple then choose your country and language if you are not automatically taken to the correct page version. Refunds are outlined at the end of section B.
Apple's terms of purchase in some countries (e.g., USA, Canada, New Zealand) are clearly "All Transactions are final.” From user comments on this forum it appears that for routine purchases Apple may make limited refunds solely at their discretion and as an exception. Apple can simply say no without having to provide a specific reason. I understand this can be frustrating but by using the service you agree to the terms.
Apple cannot remove content from a device once downloaded and has to trust that you no longer are keeping and using a copy. In countries where it does not outright say all transactions are final, Apple’s terms likely include a way to deter people from buying a bunch of items and then insisting upon right of refusal to have them refunded. In some regions Apple used to say that refunds were only granted to remedy defective or unavailable product. From what I can tell, it was recently replaced by a phrase concerning exception to cancellation rights, e.g.: “You cannot cancel your order for the supply of Content if the delivery has started upon your request and acknowledgement that you thereby lose your right of withdrawal.” Have you already successfully downloaded the content?*
Terms for most countries include a statement:
“From time to time, Apple may suspend or cancel payment or refuse a refund request if we find evidence of fraud, abuse, or unlawful or other manipulative behavior that entitles Apple to a corresponding counterclaim." It may be that certain refund requests might be considered suspicious or excessive. According to https://reportaproblem.apple.com/static/en-us/privacy.html , Apple uses an automated system to detect fraud. Your request may not have met the automated system’s criteria for a refund. In the article Apple says, “If you disagree with your final decision, contact [email protected] “ However, according to user posts on this web site the result is confusing because you receive an automated response talking about privacy issues, not refunds.