Hello ! I'm Aymeric, an independent advisor, and I'm here to help !
Just to clarify, are you referring to the Edge Wallet or your Microsoft account dashboard, available at https://account.microsoft.com/billing/payments ?
I assume you're referring to the Microsoft account, but I'd rather be sure.
When you try to delete your card, do you get a message or an error code?
Make sure you don't have any subscriptions linked to this credit card: otherwise, you won't be able to delete it.
Looking forward to your answer !