Unable to change my payment and shipping method

When I tried to make an in app purchase I got the message  “Your purchase  could not be completed. For assistance, contact iTunes Support at www.apple.dom/support/itunes/ww/.”

So I tried to change my payment method hoping that would work. But when I opened my apple id settings and clicked on payment & shipping the "edit" button was greyed out and there was no option to add a new payment method like I had been told when I tried to search up my issue.

I thought it was a family sharing issue but even that didn't have anything to do with my problem.

I have no unpaid balances, I've tried restarting my phone, signing out of my account and signing back in, and even waited a couple days to see if the issue would resolve itself.

I'm not sure what else there is to do.