How do I download apps on a new iPhone without a payment method?

I bought my brand new iphone yesterday but when I want to download some apps, it says that my apple account hasn't been used on itunes yet. Then I fill up some informations and I have to choose a payement option but I don't have any card that's why I chose "none" but then it says the same thing again and again. I tried to change my payment way by choosing "Mobile bill" but when I put a valid number it doesn't work.