Sending an SMS Message to a Phone Number AWS SNS C#

I am trying to send an SMS message to a phone number in asp.net mvc.

I am getting issue of a phone number in the publish object.

"Publish Request does not contain a defination of Phone Number."

  using Amazon.SimpleNotificationService;
  using Amazon.SimpleNotificationService.Model;
 string number = "00000000";
 string message = "Hello at " + DateTime.Now.ToShortTimeString();
 var client = new AmazonSimpleNotificationServiceClient(region: 
              Amazon.RegionEndpoint.USEast1);
 var request = new PublishRequest
 {
    Message = message,
    PhoneNumber = number
  };
  var response = client.Publish(request);