Error consuming Web Service, content type does not match binding

I am trying to consume a web service (SOAP API) but when the function is called, I get this exception: 

The content type multipart/related; type="application/xop+xml"; boundary="uuid:53c58624-2aef-492e-83df-1129be39d10d"; start=""; start-info="text/xml" of the response message does not match the content type of the binding (text/xml; charset=utf-8). If using a custom encoder, be sure that the IsContentTypeSupported method is implemented properly. The first 1024 bytes of the response were: '--uuid:53c58624-2aef-492e-83df-1129be39d10d
Content-Type: application/xop+xml; charset=UTF-8; type="text/xml"
Content-Transfer-Encoding: binary
Content-ID:

2021-06-24T14:25:45.877-04:00base.Channel.exportDevicesAsync(request)COMPLETED
--uuid:53c58624-2aef-492e-83df-1129be39d10d
Content-Type: application/octet-stream
Content-Transfer-Encoding: binary
Content-ID: <[email protected]>
Content-Disposition: attachment;name="130_1624559145'.

I'm using .NET Core 3.1 and used this Medium Article to set up my WSDL files/Connected Services. I have tried adding the following to my App.config file (though I'm not sure if I have it actually attached, it still has the green + sign). But it didn't seem to work. 

I have also tried:

BasicHttpBinding binding = new BasicHttpBinding();
binding.MessageEncoding = WSMessageEncoding.Mtom;

But it doesn't seem to work because .MessageEncoding does not seem to be supported in .NET Core 3.1 and only in .NET Framework. So, does anyone know of a fix to the exception or to allow the binding to be encoded as Mtom?