exports.handler = function(context, event, callback) {
  // List all blocked phone numbers in quotes and E.164 formatting, separated by a comma
  let numberBlock = event.block || [ "+xxxxxxx", "+xxxxxxx" ];
  let twiml = new Twilio.twiml.VoiceResponse();
  let blocked = true;
  if (numberBlock.length > 0) {
    if (numberBlock.indexOf(event.From) === -1) {
      blocked = false;
    }
  }
  if (blocked) {
    twiml.reject();
    callback(null, twiml);
  }
  else {
     const response = new Twilio.Response();
     // Set the status code to 200
     response.setStatusCode(200);
     return callback(null, response);
  }
};