How to set content-Type on WCF request - soap

Question

My issue is that a testing app like Google Postman (awesome tool, found here) can send the message.
When I send the message it's always refused (the exact same message) because nonse is 'expired'.
So there must be something different about how I'm sending it...
There is... Content-Type is different, for one... but not sure if that's why...
I've seen some hints about accessing endpoint behaviours like:
var whb = client.ChannelFactory.Endpoint.Behaviors.Find<WebHttpBehavior>();
But that only allows me to choose between xml and json.
whb.AutomaticFormatSelectionEnabled = false;
whb.DefaultOutgoingRequestFormat = WebMessageFormat.Xml;
I have a wsdl:
http://caqh.org/SOAP/WSDL/CORERule2.2.0.wsdl
I need to call the WCF service's RealTimeTransaciton with headers that that are:
Content-Type: application/soap+xml;charset=UTF-8;
Currently, by default I suppose, the call includes headers;
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
and Content-Type doesn't seem to be set.
So I tried to affect the headers of the request...
var addressHeaders = new List<AddressHeader> {
AddressHeader.CreateAddressHeader("Content-Type", "", "application/soap+xml;charset=UTF-8;"),
AddressHeader.CreateAddressHeader("Cache-Control", "", "no-cache"),
AddressHeader.CreateAddressHeader("Accept", "", "application/soap+xml;charset=UTF-8;")
};
var client = new CORETransactionsClient(binding, new EndpointAddress(new Uri(url),addressHeaders.ToArray()));
But to my surprise, the result of this is that these 'headers' are added within the soap Envelope headers, and not the headers for the transport!
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<s:Header>
<Content-Type>application/soap+xml;charset=UTF-8;</Content-Type>
<Cache-Control>no-cache</Cache-Control>
<Accept>application/soap+xml;charset=UTF-8;</Accept>
<o:Security s:mustUnderstand="1" xmlns:o="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
etc.... lol
My web.config service model:
<system.serviceModel>
<bindings>
<customBinding>
<binding name="CoreSoapBinding">
<textMessageEncoding messageVersion="Soap12" writeEncoding="UTF8" />
</binding>
</customBinding>
</bindings>
<client>
<endpoint address="https://my_vendor_url_for_service_that_is_Axis2_based" binding="customBinding"
bindingConfiguration="CoreSoapBinding" contract="CoreRule.CORETransactions"
name="CoreSoapPort"
endpointConfiguration="">
</endpoint>
</client>
</system.serviceModel>
How I call:
var msg = Create270X12Message(requestReferenceId, senderId, receiverId, requestDateStr, productionCall, prettyOutput);
var envelope = new COREEnvelopeRealTimeRequest
{
CORERuleVersion = "2.2.0",
Payload = string.Format("<![CDATA[{0}]]>", Convert.ToBase64String(Encoding.UTF8.GetBytes(msg))),
PayloadID = requestReferenceId.ToString(),
PayloadType = CoreRule2PayloadType_270_5010,
ProcessingMode = CoreRule2ProcessingMode_270_5010,
ReceiverID = receiverId,
SenderID = senderId,
TimeStamp = requestDateStr
};
var client = CreateRealTimeOnlineProxy(urlMissouiri, username, password, requestDateStr);
var response = client.RealTimeTransaction(envelope);
How can I add my collection of headers to the request itself, instead of the SOAP Envelope headers?