远程服务器返回意外响应：（400）调用wsdl方法的错误请求

Question

您好，下面是发生错误的代码“远程服务器返回了意外的响应：（400）错误的请求” 。我不知道我要去哪里错了。将WSDL URL添加到我的解决方案后，我便能够获取所有方法。但是为什么我会收到此错误。

        EXOZEndpointPortClient client = new EXOZEndpointPortClient();
        client.ClientCredentials.UserName.UserName = username;
        client.ClientCredentials.UserName.Password = password;
        client.Endpoint.Name = "EXOZEndpointPortSoap12";
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
        GetAvailabilityRequest getAvailabilty = new GetAvailabilityRequest();
        getAvailabilty.FromDate = System.DateTime.Now; // should be Datetime (ISO 8601)
        getAvailabilty.ToDate = System.DateTime.Now.AddDays(7);// should be Datetime (ISO 8601)
        getAvailabilty.ProductOptionQuantities = new ProductOptionQuantity[] { new ProductOptionQuantity { id = 1, Value = 39490 } };
        var response = client.GetAvailability(getAvailabilty);

下面是我的web.config

<system.serviceModel>
<bindings>
  <customBinding>
    <binding name="EXOZEndpointPortSoap12">
      <textMessageEncoding messageVersion="Soap12" />
      <httpsTransport/>
    </binding>
  </customBinding>
</bindings>
<client>
  <endpoint address="https://x.x.net.au/v2/exoz"
    binding="customBinding" bindingConfiguration="EXOZEndpointPortSoap12"
    contract="TicketsMatesTransactionalAPI.EXOZEndpointPort" name="EXOZEndpointPortSoap12" />
</client>