2. Try to do the call out from developer console.
The debug log will include the CALLOUT_REQUEST and CALLOUT_RESPONSE messages that will include the raw SOAP request and response.
Log level “callout” Includes the request-response XML that the server is sending and receiving from an external web service. Useful when debugging issues related to using Lightning Platform web service API calls or troubleshooting user access to external objects via Salesforce Connect.