How to interact with an API that uses GET and POST?

I am going to attempt to have my autoit script do some Cisco Unity Voicemail operations as part of the script. (Creating a user's voicemail box, setting the voicemail PIN, etc)

Here is a link to the API examples given by Cisco.

http://docwiki.cisco.com/wiki/Cisco_Unity_Connection_Provisioning_Interface_(CUPI)_API_--_Examples_of_Basic_Operations#Creating_a_User

However I don't know how I go about running a command that takes advantage of those GET and POST commands, or how to pass the other data (the XML string, etc)