Opt out of payment method

Also note, if you do not have a valid payment method on your account, you will not be able to download apps from the App Store. That includes any free app, which has "in-app purchases."

I have never been charged anything for a free app, EVER. The only time you would be charged for something associated with a free app is if you choose to purchase something in the app, which as I said are called in-app purchases.

Go to settings> your name (Apple ID)>payment and shipping>payment method tap on it and remove payment method

Depending on your region, you may not be able to opt out of having a payment method on file.