Hi DJJimmy8000,
Thanks for posting in Apple Support Communities! Since you're unable to add a payment method, we suggest restarting your device to see if anything changes. Restarting can fix many issues:
- "Press and hold either volume button and the side button until the power-off slider appears.

2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo."
-Restart your iPhone
If you're still unable to edit your payment information, try while connected to another network or while using another device. This article may help: Change, add, or remove Apple ID payment methods
Should it continue, contact Apple Support for further assistance.
Cheers!