i want to get an app but it says my billing information is wrong

It pops up with a notification saying that my billing information is incorrect I enter in my billing information again and it says that it's in correct. Then I will look for it at the none button for billing information and I cannot find it so in conclusion I need help finding out how I can get rid of my billing info. It says I need to change my billing information to purchase apps music and other things I need help