How to consume 3rd party web service from a WCF service

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C#

WCF

WCFService

I have written a simple Duplex WCF service and client. The client instantiates a proxy, opens & connects to the WCF service, then passes a request to the service AddRequest method. The WCF service receives the request. . .

(**placeholder**)

. . .the WCF service sends a default string response to the client on the same callbackchannel that the client is connected to. The client callback event handler then saves the WCF service defaults string response, disconnects & closes the proxy.
Simple, two-way communication, all working nicely.

I now wish to make a call to a 3rd party web service at (**placeholder**) and return the response from that, instead of the default string response. I am struggling to get the 3rd party endpoint correctly defined (the config settings for the 3rd party web service generated when the service reference was added). Could anyone kindly give me a steer on how best to approach this?

Many thanks

What I have tried:

Attempted to instantiate the class that makes the 3rd party web service call (this is working perfectly in another application), but encountering problems

"System.InvalidOperationException: Could not find default endpoint element that references contract 'ServiceReference1.ThirdPartyService' in the ServiceModel client configuration section. This might be because no configuration file was found for your application, or because no endpoint element matching this contract could be found in the client element."