Error calling WCF service

Context: .Net 3.5, C#, WCF

Was getting this error message when trying to call a WCF service's method:

The message with Action 'blah' cannot be processed at the receiver, due to a ContractFilter mismatch at the EndpointDispatcher. This may be because of either a contract mismatch (mismatched Actions between sender and receiver) or a binding/security mismatch between the sender and the receiver. Check that sender and receiver have the same contract and the same binding (including security requirements, e.g. Message, Transport, None).

In my case it was caused by the old version of the service deployed on the server. I was calling a function which was in the service's contract on the client side, but was not there on on the server side. To solve the problem deploy the latest version of the service.