def validate_number(phone_number)
      phone_number = phone_number.gsub(/\D/,'')
      raise InvalidPhoneNumberException, "Invalid Phone Number #{phone_number}" if phone_number.length < 4 || phone_number.length > 15
      phone_number
    end
def validate_number(phone_number)
      phone_number = phone_number.gsub(/\D/,'')
      raise InvalidPhoneNumberException, "Invalid Phone Number #{phone_number}" if phone_number.length < 4 || phone_number.length > 15
      phone_number
    end
International numbers can vary in length as opposed to the standard US 10 digit number
 So we can't effectively validate based on length. Instead, let's make sure we have at
 least 4 digits and at most 15 since E.164 recommends at most 15 digits minus country code
 for the phone number (http://en.wikipedia.org/wiki/E.164)