iTunes “billing info” payment problem

I haven’t made many iTunes purchases recently. Last night, I tried to purchase a song. I signed in with my Apple ID and verified I wanted to make the purchase. But instead of simply charging my Apple account (which has money in it), I got a box telling me I needed to verify my billing info and select a payment method. But when I tried to do that, I could never select my Apple account. I don’t want to pay with a credit card. No matter what I tried, I just kept going through the same loop. How can I make my purchase and use money I already have in my account?