I'm developing a use-case diagram for a system that uses several external APIs.
The system should identify when a customer made an EFT(Electronic Fund Transfer) payment to a merchant's bank account and update the system accordingly. An external banking API is used for that purpose.
The EFT payment is not a direct interaction with the system, but it leads to the banking API to identify the payment, and there are a series of other events initiated by the system itself.
Since the "Make EFT Payment" happens outside the system, it cannot be a valid use case. However, the rest occurs within the system, starting with identifying the payment.
How to implement this kind of scenario in a use case diagram?
Update:This is a simplified version of the system behavior:
The system allows merchants to upload invoice details to the system. These invoices are paid via electronic fund transfers only. The system uses a banking API to identify EFT payments made to those invoices by customers using invoice details uploaded. A discount needs to be applied if the system finds the customer is an eligible member. The system uses the banking API to charge the discount amount from the merchant's account and return it to the customer's account.