If you are looking to cancel an order go to the email with the purchase ID attached to it or within the email from Apple. You should be able to "Report" the purchase and therefore refund or cancel the purchase.
The issue and preferred resolution, in GetHuman756653's own words:
The problem I ran into: I did not mean to finalize order
I trust that American Eagle Outfitters will make this right and come up with a resolution that is fair.
Help me with my issue
Follow this to see how it gets fixed
Find similar issues & what fixed it
Follow 3 or more issues like yours to increase the chances that another customer helps you find the right answer.