I want to change my payment method to none but I’m unable to do that . Am asked to purchase a app before I can change my payment method

Hi,

Contact Apple directly > Contact - Official Apple Support

1. If you owe Apple for any subscriptions, you cannot remove your payment method to none.
2. If you have ANY apps on your phone, even free ones which offer in-app purchases, you cannot remove your payment method.

The reality is there are almost no apps you can download or keep on your phone without a valid payment method.