Thanks for posting your question in the Microsoft Q&A forum. And sorry for the inconvenience caused.
Virtual or pre-paid credit or debit cards aren't accepted as Payment for Azure subscriptions and unfortunately you won’t be able to sign-up for an Azure subscription without using a Credit card. Also, American Express (AMEX) is no longer supported as a Payment Instrument for Azure accounts.
May this article help you: Troubleshoot a declined card at Azure sign-up
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