Twilio call phone number masking using C# API

Question

I need to connect two customer via voice call, but I want to hide original phone number from each other. I'm planning to implement it using twilio. My current progress is up to making a call from twilio.

const string accountSid = "ACXXXXXXXXXXXXXXXXXXXX";
            const string authToken = "fXXXXXXXXXXXXXXXXXx";
            TwilioClient.Init(accountSid, authToken);

var to = new PhoneNumber("+91XXXXXXXXXXXX");
            var from = new PhoneNumber("+1XXXXXXXX");
            var call = CallResource.Create(to, from,
                url: new Uri("http://demo.twilio.com/docs/voice.xml"));

Now I am not getting the part where I need to mask phone number, and adding two party's to have a voice conversation via twilio.

I am confused how to start, I've gone through https://www.twilio.com/docs/sms/tutorials/masked-numbers-csharp-mvc , but not able to understand it properly.

Thanks in advance.