I have redeemed a apple ID code that I have bought on a website and it worked. Although when I tried to purchase a in app product it says to 'Contact iTunes Store Support to complete this transaction'. What should I do and the game is 'Puzzle and Dragons'.
Contact iTunes store support won't help anything but lock your account permanently. I'm in the same situation as you and they just keep saying you violate Apple legal regulation and unless you live in Japan, have a Japan credit card and proven billing address, will never be able to do IAP.