Jay,
Yes is possible to receive a SOAP message in a WCF method, but what I think you want is to read the header variables in the inbound request.
On the host side, create an object from this:
System.ServiceModel.OperationContext.Current.IncomingMessageHeaders
This will return an indexed collection of the inbound message headers sent from the client, and you can read it this way:
OpContext.IncomingMessageHeaders(0).ToString