WCF Web Service can't access service name in Web Config

This is my first web service and I am trying to follow a tutorial on creating a custom authentication for a web service, am stuck as I'm getting this error:

The value 'WcfOrderingService.Services.AuthenticationTokenService' is invalid according to its datatype 'serviceNameType' - The Enumeration constraint failed.

web config:

      <service name ="WcfOrderingService.Services.AuthenticationTokenService"
           behaviorConfiguration="ServiceBehaviourHttp">
    <endpoint address="" behaviorConfiguration="WcfOrderingService.AuthenticationTokenServiceAspNetAjaxBehavior"
      binding="webHttpBinding" contract="WcfOrderingService.Services.AuthenticationTokenService.Authenticate" />
  </service>

.svc.cs -

namespace WcfOrderingService.Services
{
[ServiceContract]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class AuthenticationTokenService
{
    [WebInvoke(Method = "POST", RequestFormat = WebMessageFormat.Json,
    ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Bare)]
    [OperationContract]
    public string Authenticate(Credentials creds)
    {
        ICredentialsValidator validator = new CredentialsValidator();
        if (validator.IsValid(creds))
            return new TokenBuilder().Build(creds);
        throw new InvalidCredentialException("Invalid credentials");
    }
}

}

I have tried most things I have found online, variations of the service name etc but cant find an answer.

Thanks in advance.