public function extractNationalDestinationCode($number = '', $countryCode = null)
 {
     // all numbers have the same length
     if (strlen($number) != $this->numberLength) {
         return;
     }
     //landlines + voip
     if (strpos($number, $this->landlinePrefix) === 0 || strpos($number, $this->voipPrefix) === 0) {
         $phoneNumber = new PhoneNumber();
         $phoneNumber->setSubscriberNumber($number);
         $phoneNumber->setIsMobile(false);
         return $phoneNumber;
     }
     //mobile
     foreach ($this->mobileRules as $rule) {
         if (preg_match('/^' . $rule . '.*$/', $number)) {
             $phoneNumber = new PhoneNumber();
             $phoneNumber->setSubscriberNumber($number);
             $phoneNumber->setIsMobile(true);
             return $phoneNumber;
         }
     }
 }