It will not let me add a a card for by subscriptions on my iphone

Change, add, or remove a payment method

You can edit your payment information in Settings on your iPhone or iPad, or in the App Store on your Mac.

Change, add, or remove Apple ID payment methods

Still if the problem exists please follow the below instructions.

See what forms of payment are accepted in your country or region.

If you can't make purchases or update apps, including free apps, you need to update your payment method or add a new one. If you already verified that a payment method is available in your country or region and you're still having trouble, contact apple suport. https://getsupport.apple.com/?caller=ikb

Thanks