Unable to purchase free apps even though no credit card on Apple ID

Hello

We have set up an Apple ID with no credit card attached. Yet when I use this to purchase my first free app, the prompts take me through the 'This is the first time you have used your ID to purchase' screens where I accept disclaimers etc; then it asks me to confirm my details, including credit card details. As this Apple ID has no credit card details, then it asks me to input some. I can only choose Visa or Mastercard; the 'none' option is not available.

Yet when I look at the instructions on how to set up an Apple ID with no credit card, you normally get asked to choose between 'Visa', 'Mastercard', or 'None'.

It seems we have set up this Apple ID before the 'None' option existed, yet we've managed to set it up with blank credit card fields.

Now it seems to be 'stuck' in credit-card land.

Is there any way to revert it to a non-credit card Apple ID so that I can buy free apps?

Any help appreciated