Connecting to a SOAP Web Service

I am using wp_remote_get ( &url , &args ) to connect to a legacy application (we have control of) via an exposed web service. Although I am able to connect to it, I am having problems understanding the mechanism to call methods within it and pass parameters to it. I understand the array construct but not sure what to poke where. I'm close , but no cigar. Note the service is SOAP (1.2) and not JSON.

If you could point me in some explicit examples I could follow, this would be of great assistance.