How to get app store refund?

Hello All,
How do you get a refund from the app store? I followed the "report a problem" link in the invoice email from Apple. Once I managed to finally login I end up at a page where there does not appear to be any option to report that the app is incompatible with voiceover nor is there any obvious way to request a refund for this reason.
So just how do you folks do it? BTW: this is the Canadian app store.
Thanks for your help.