Hi Krit R.
the service explorer shows synchronous Soap web service APIs.
The web service ExternalServicePerformingAndChargingSystemRequestServiceConfirmationMaintenanceIn is an asynchronous web service released for the pre-packaged application to application scenario "Customer Contracts - Managed Service Consumption Integration" only. You find further information about the integration scenario on SAP help: SAP Business ByDesign 1511 Integration Scenarios.
To enable the communication scenario "Customer Contracts - Managed Service Consumption Integration", you have to request to install the ByD Add-on "Add-on Managed Service Consumption Integration for Customer Contracts" and answer the business configuration question "Do you want to receive service confirmations electronically from an external system over electronic data exchange?" with Yes.
If this is done, you can create a communication arrangement for scenario "Customer Contracts - Managed Service Consumption Integration".
Interface documentation, access URL and WSDL are available in the communication arrangement as soon as created.
Best regards,
Knut