code: public String extractSubscriberNumber() {
          
  		final String nationalSignificantNumber = PHONE_NUMBER_UTIL.getNationalSignificantNumber(number);
  		final String subscriberNumber;
  
  		int areaCodeLength = PHONE_NUMBER_UTIL.getLengthOfGeographicalAreaCode(number);
  		if (areaCodeLength > 0) {
  			subscriberNumber = nationalSignificantNumber.substring(areaCodeLength);
  		} else {
  			subscriberNumber = nationalSignificantNumber;
  		}
  
  		return subscriberNumber;
      }
docs: {@inheritDoc}