Recently my credit card for Azure expired. I have to replace it with a new card. But when I added my new card and try to delete my old credit card, Azure pop up an error saying "Cannot delete payment method(s)" and indicates that the card is in use.
I was trying to delete credit card from "Cost Management + Billing" - "Payment methods" screen.
The reason why Azure won't let me delete my old card is because it was bind to my Azure subscriptions. However, on this screen, there are no way to let me manage binding relationships between credit cards and subscriptions.
In order to bind subscriptions to use the new card, we need to go to "Subscriptions", click on any one of the subscription, and go to "Payment methods", here we got a very similar UI for credit card management, but with a few more buttons. Just select the new card, click "Set active", after a few minutes. You would be able to delete the old card now.
I think Azure portal can have some usability improvements, like managing payment methods within only one screen, or at least show a button or link for manage payment-subscription bindings. So that users won't have to click around to find another place for updating payment relationship to subscriptions.