How to get response from CodeUnit Procedure from online Business Central, using postman

I have the following code unit on BC, that I have exposed on web service under service name ReportService. When supplied with a specific employee number, It should give a report response in base64.

I have tried following tutorials on youtube, Microsoft learn, and personal blogs, but seems like I am missing a step.

Accessing it via SOAP on Postman, I get the below response, through with no base64.

When I try to access it via Odata as an unbound action, this is the error am getting

How do i get the specific (base64) response from the code unit procedure, via postman?