Call a soap HTTP_URL_POST_STMF_XML RPGLE

I'm trying to call a "HTTP_URL_POST_STMF_XML", because the soap string that we have it could be bigger than 65500 characters.

My problem is that I don't know how to call it right. Always the call HTTP_URL_POST_STMF_XML return to me "500".

My call is the next one:

rc = HTTP_URL_POST_STMF_XML(

%trim(urlWS)

: %TRIM(filename)

: *NULL

: %paddr(Incoming)

: %addr(Incoming)

: HTTP_TIMEOUT

: HTTP_USERAGENT

: 'text/xml'

: 'actionWS');

also I Tried to use the exercise nº 7 of Scott Klement but I don't know how to use. what I am doing wrong?

thanks in advance!!