Can't form the correct SOAP method from the incoming message template?

Question

Computer networks

???
[WebMethod(MessageName="receiveMessage", Description = "The method is designed to receive PSP messages from RRP")]
public Status receiveMessage(string systemID, string document, string documentType)
{
Status tutu = new Status();
return tutu;
}
Please tell me who understands the services, at the top of the message that they send me, the method is launched but the input variables are null
PS the template of the incoming message cannot be changed (I myself know if you remove it at all P: then it works, or vice versa put this tag in the incoming variables, then everything works)
implement the extension and and replacing the wrong input with the right one does not help, because After that, the server does not respond at all.

Answer 1

public Status receiveMessage( [XmlElement(Namespace = "")] string systemID,
similarly for other attributes, i.e. remove the namespace for elements...