I just bought an iTunes card and I'm trying to buy a game and it keeps saying your purchase can not be made please contact the iTunes support. Why does it keep doing this?

I Just bought an iTunes card from the store and I went to go buy a game and it's saying my purchase can not be made please go to iTunes support. But this keeps happening and I can only download free apps no apps that cost money and I did looked it up on google and they say to make sure there is no restrictions And I did and it's still doing it. Please help