For SOAP request and response pairs, the SOAP envelope payload is required.
<?xml version="1.0" encoding="UTF-8"?>
If there is a need to add a base path to the VSM, you can do it by adding a POST URL as the first line in the request file:
POST /aaa/bbb/ccc HTTP/1.1
SOAP Payload here.
Note: there must be an empty line to separate the body from the header.
A basepath can also be added or modified in the VSM, Listener step after the Virtual Service is created.
While selecting the Data Protocol Handlers (DPH), remove the REST DPH added and leave the SOAP DPH.
There are few SOAP payloads examples available in the DevTest Portal, under Create, Virtual Service, RR Pairs.