Its entirely possible you may not be able to get a refund. Your purchase may in fact not be eligible for one.
The terms of service of the iTunes and app Store clearly state all sales are considered final. Refunds are given under Apple's own discretion, and there's nothing that says all requests should be automatically granted.
If the https://reportaproblem.apple.com website is not being cooperative, you can contact iTunes Billing directly and see if they are willing to make the exception for you and your specific situation: iTunes Store - Contact Us - Official Apple Support