Reg. CPQ integration with EBS using REST Services

Hi,

We are working on a POC for Client Demo purpose to Integrate our internal DEMO CPQ environment with EBS system using the Vanilla "PROCESS_ORDER" REST service.

As a part of that, we got the Order Header templates from our EBS system for PROCESS_ORDER, built a payload in CPQ using the BML script and calling the REST service using the "urldatabypost" function,

But, somehow our EBS system is NOT recognizing the request and ending with "10.5.1 500 Internal Server Error"

So, we just wanted to know, can't we integrate CPQ & EBS environments with available REST services directly without any customization.