WCF authentication error with mutual SSL using certificates

I am trying to use a service published by another company. The specifications for authentication and communication are:

• Soap
• HTTPS with two-way SSL authentication (2-way SSL)
  • Use the public certificate they sent us (which I use as ServiceCertificate)
  • Use the private certificate they created for us (which I use as ClientCertificate)
• WS-Security with UsernameToken

Here is the code I have attached so far:

WSHttpBinding binding = new WSHttpBinding(SecurityMode.Transport);
binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.Certificate;
binding.SendTimeout = binding.CloseTimeout = binding.ReceiveTimeout = binding.OpenTimeout = new TimeSpan(0, 15, 0); // 15 minutes

Uri uri = new Uri(input.ServiceAddress);
EndpointAddress endpointAddress = new EndpointAddress(uri);

// Client creation
using (Client client = new Client(binding, endpointAddress))
{
    client.ClientCredentials.ClientCertificate.Certificate = input.PrivateCertificate;
    client.ClientCredentials.ServiceCertificate.DefaultCertificate = input.PublicCertificate;

    client.Open();

    // Service call
    ResponseType response = client.ServiceCall(params);
}

I get this error when calling the service:

An error occurred while making an HTTP request to the service . This may be due to the server certificate not being properly configured with HTTP.SYS in the HTTPS case. This can also be caused by mismatched security bindings between client and server.

Things I've tried:

• Add the following line of code: "System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Ssl3;"
  • Find solutions on this and this
• Register public certificate in port using netsh
  • Use this command: "netsh http add sslcert ipport=0.0.0.0:443 certhash= certificate thumbprint appid={ application GUID }"
  • Based on another problem we had in another project

I don't know how to fix this, I don't know anything about it! Have searched a lot and everything I've tried doesn't work!