I tried to get a refund from Apple once, for a fraudulent app, but I never heard back. So I disputed the charge with Visa. I thought I'd solved the problem until Apple locked me out of the app store. The only way to get back to installing apps (even free ones) on my phone, if I remember right, was to use a new credit card.
Later on I did successfully get a refund for being charged twice for the same content when I bought it again on a family-shared device. Free tip: in-app purchases apparently aren't sharable to the family.
Counter anecodote: I got a (Mac, not iOS) app refunded within 2 days because it didn't function as well as I thought it would (email client). No hassle.
