Error retrieving XML, but works in Validator

[Transformations]

I’ve run a couple of tests, but the phone message each time is an error. Here is what I am getting from the call log.
Attempting to fetch http://75.151.51.219:82//test.xml
HTTP/1.1 405 Method Not Allowed - http://75.151.51.219:82//test.xml
DocumentParser::FetchBuffer - could not open URL: http://75.151.51.219:82//test.xml
DocumentParser::FetchDocument - exiting with error result 2
errno: 203 uri http://75.151.51.219:82//test.xml

When I use the xml validator on your website with that same URL it picks up the xml fine and validates it. Obviously, I am using a test URL on our side, and I expect that is the issue.
Can you help?

[support]

Hi,

It seems that you are trying to place outbound calls using a static XML file as a start_url. Please note that as part of the outbound call control flow, Plum Voice sends a POST request to your start_url, passing parameters defined in the Outbound API such as callee_type, phone_number, and more.

As such, your start_url must be in the form of a dynamic VXML script that can accept POST requests such as .php or .aspx.

Please refer to the Outbound Developer's Guide for more info.

Regards,
Plum Support