call out that prepaid cards are not accepted (#60779)

Co-authored-by: Sunbrye Ly <56200261+sunbrye@users.noreply.github.com>

Author: dhruvchand

content/billing/reference/supported-payment-methods.md

@@ -13,6 +13,9 @@ category:
 
 ## Metered or usage-based billing options
 
+> [!NOTE]
+> Prepaid credit/debit cards are not accepted as a valid form of payment.
+
 The supported payment methods for metered billing:
 
 * Invoice – Managed accounts only