why i cant download free app (war robbots) just now i download his tell me to billing why?

If you can't choose None when you edit your Apple ID payment information

1. If you have an unpaid balance or payment due
2. If you have a subscription that automatically renews
3. If you're using the iTunes Store or App Store for the first time
4. If you are not in the country or region you’re creating an Apple ID for
5. If you changed your country or region
6. If you're a part of Family Sharing

Before you can download apps, Update apps, buy apps and music, change or remove you card details or payment methods on iTunes / App Store

You need to check what is the outstanding bill on App Store purchases by doing the following:

1. Open the “Settings” in iOS, then go to ‘iTunes & App Store’ and then select your Apple ID
2. Choose “View Apple ID” to access the Account Settings page
3. 
4. In the Account Settings section, go to “Purchase History” and scroll through the list to find any item with an outstanding balance – this is what must be paid before you can change your payment information
5. Once the balance payable is zero. Give it 2-3 working days.