Hi ray.rayy,
welcome to this Apple (user-to-user) Community!
Re: " I got charged for a 3 day free trail cancelled on the day I downloaded the app because it wasn’t working spoke to Apple about a refund showed them proof of the 3 days free Trial trial lucky I had a screenshot but still denied refund. "
A free trial needs to be cancelled at least 24 hours before it expires in order to not be charged.
As the app wasn't working, seems your cancellation didn't work either, as you were charged:
(I notice your screenshot shows "Cancel anytime" at the bottom)
ie: You may still need to cancel the subscription if it is active, in order to not be charged in the future.
See: If you want to cancel a subscription from Apple - Apple Support
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Re: I had a screenshot but still denied refund. "
If Apple merely passed your payment on to a third-party for you, (much like a bank does) then Apple doesn't have your money in order to refund it. (ie: Your app transaction is not the same as purchases of Apple's own products.)
As far as I know: The best source of help for a product not made by Apple (a third-party product) is the company or person who made it—its vendor or developer: You can: Contact a third-party vendor - Apple Support
or see How to contact an app developer - Apple Support
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If (after contacting the vendor or developer of the free trial app), you haven't been able to negotiate a satisfactory result, or a refund:
You can Find the URL for content to report a concern - Apple Support
Where to report a problem: https://reportaproblem.apple.com/?s=6
All the best :-)