Message type: E = Error
Message class:  FKKEXC - Message Class for External Payments 
Message number: 040
Message text: Only credit cards are supported
Payment <(>&<)>1 contains a payment card that is not of the category
"credit card" (category code = '1')
Such payment cards are not supported in the standard.
XI message cannot be processed.
Implement your own logic in event 6200 and set the parameter <LS>
E_FURTHER_CARDS</> to avoid the error message.
Error message extract from SAP system. Copyright SAP SE.
The SAP error message FKKEXC040: Only credit cards are supported typically occurs in the context of SAP Convergent Charging or SAP Contract Accounts Receivable and Payable (FI-CA) when a payment method that is not a credit card is being used in a scenario where only credit card payments are allowed.
Cause: Payment Method Configuration: The payment method being used for the transaction is not configured to accept anything other than credit cards. This can happen if the system is set up to only allow credit card transactions for certain types of billing or payment processing. Transaction Type: The specific transaction or billing type may be restricted to credit card payments only, leading to this error when another payment method is attempted. User Input Error: The user may have inadvertently selected a non-credit card payment method when processing a transaction that requires a credit card.
Solution: Check Payment Method: Verify the payment method being used in the
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