It looks like you using SOAPui to create request xml. This app always adds invisible chars at the end of each line. Delete them.
Also try to unformat your request, e.g. make it in one line. For unknown reason Nav threats linebreake between certain tags as error (throws http 500). I just forgot which tags (header and body may be). The rest linebreaks are fine.
And SOAPAction header is mandatory so use it or you will get wsdl in response all the time.
P.s. beta of SOAPui works fine with Nav and supports NTLM so you can use it to test different request xml and find which format is correct.