How do i get a refund?

Take the gift card and proof of purchase to the seller and see if you can return it.

You can try iTunes Support if you bought it from Apple online (not eBay or other sites) in case they can do anything (no guarantees): https://www.apple.com/support/itunes/ww

Did you get a Gift card? If the funds are already added, you need to contact iTunes Support using the above link.