Error: Server did not recognize the value of HTTP Header SOAPAction

Hello,

I know that ASMX technology is considered legacy stuff. There's no need to lecture me on that point.

I am jumping in on an existing project that uses web services. (Editorial statement: Yuck!) When I test the webservice, I call up a similar URL to this:
https://OurServerVisibleToThePublic.com/FolderWithASMXFile/TheASMXFile.asmx

When I do this I get a page that contains all of the webservices we have defined. When testing, I click on one of them, a new page opens with parameters, I give it credentials and the XML that I am expecting is returned.

Now, I am attempting to call one or more web services from an ASP.NET application. The code looks like:
DIM WS as new CompanyWebServices.WebServicesClassName
GetData.DataSource = WS.MyWebServiceName(param1, param2, param3)

Unfortunately, the second line bombs, producing this fun error to solve:
Error: Server did not recognize the value of HTTP Header SOAPAction

At the top of the WSDL file, I have an attribute with a TargetNameSpace. The current setting is similar to this:
targetNamespace="https://OurServerVisibleToThePublic.com/FolderWithASMXFile"

When the app encounters the second line (i.e., WS.MyWebServiceName) I generate this error:
Message=System.Web.Services.Protocols.SoapException: Server did not recognize the value of HTTP Header SOAPAction: https://OurServerVisibleToThePublic.com/FolderWithASMXFile/MyWebServiceName.
at System.Web.Services.Protocols.Soap11ServerProtocolHelper.RouteRequest()
at System.Web.Services.Protocols.SoapServerProtocol.Initialize()
at System.Web.Services.Protocols.ServerProtocol.SetContext(Type type, HttpContext context, HttpRequest request, HttpResponse response)
at System.Web.Services.Protocols.ServerProtocolFactory.Create(Type type, HttpContext context, HttpRequest request, HttpResponse response, Boolean& abortProcessing)

* * * *

Does anyone know what I should specify in my TargetNameSpace? Does anyone actually like to troubleshoot web services? Thanks.