How do I report for refund for being charged for free trial?

It is also likely that you signed up for the free trial directly with YouTube and that subscription is not being managed by Apple. It is easy to tell if your subscription is being managed by Apple, as you will be able to find it at Settings > [your name] > Subscriptions:

View or cancel app subscriptions on iPhone - Apple Support

If you did sign up directly with YouTube and bypassed Apple's ability to manage the subscription, then you will need to cancel it by going to the YouTube site and you would also have to deal with them for any refund.

If you got an email receipt, use the 'Report a Problem' link in it; otherwise, click here and ask the iTunes Store staff for a refund.

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