iPhone 4 signing in issues

So I just got my iPhone and I made a new Apple iTunes account and I verified my account through email then I tried to download a game and it says please sign in so I tried signing it and it said I need to complete my registration and to put in bank details , which I already did signing up... so I put them in again and this time it came back with " card declined, payment method didn't work" blah blah blah.. I cannot download games and I cannot access my emails or apples iTunes I cannot sign in it wot let me can someone help? Thank you