How do I send keys to phone field using webdriver in firefox?

   package erjan.testNG.personal_cabinet;

    import java.util.concurrent.TimeUnit;
    import org.openqa.selenium.By;
    import org.openqa.selenium.WebDriver;
    import org.openqa.selenium.WebElement;
    import org.openqa.selenium.firefox.FirefoxDriver;
    import org.testng.Assert;
    import org.testng.annotations.Test;
    import org.testng.annotations.BeforeMethod;
    import org.testng.annotations.AfterMethod;

    public class Login_test {
      WebDriver firefox ;
      @Test
      public void f() {
          WebElement login_form

 = firefox.findElement(By.id("login-form")) ;

      WebElement phone_field = firefox.findElement(By.className("phone-username")) ;

      WebElement password_field = firefox.findElement(By.xpath("//input[@type=\"text\"]"));

      Assert.assertNotNull(login_form) ;
      Assert.assertNotNull(phone_field) ;
      Assert.assertNotNull(password_field);


      phone_field.sendKeys("4457653245");

      String x = phone_field.getText() ;
      System.out.println("here we go!!!!!!!!! " + x) ;


  }

  @BeforeMethod
  public void beforeMethod() {

      firefox = new FirefoxDriver();
      firefox.get("http://ift.tt/19BNkbL");

  }

  @AfterMethod
  public void afterMethod() {
  }

}

I see firefox open but i don't see my number getting inserted in the phone field! or maybe it happens fast? or maybe because it has to be standardized in some way?

should I somehow "slow down" the input to see it typed in number-by-number? should I use explicit wait?