Hello Frankmessann,
Try adding a payment method to your account before you remove the current payment method in order to resolve this issue. Because you have an active subscription, you won't be allowed to remove your current payment method unless you add another one. The article you referenced explains how:
If you need to change or update your Apple ID payment method - Apple Support
Update your payment method on your iPhone or iPad
1. Open the Settings app.
2. Tap your name.
3. Tap Payment & Shipping. You might be asked to sign in with your Apple ID.
4. Tap Add Payment Method, enter the new payment method, then tap Done.
5. Tap Edit.
6. Tap the red delete button next to the old payment method, then tap Delete.
Best Regards.