code: public Set<String> getListPhoneNumbersInBlackList() {
  		 List<Blacklist> listPhoneNumbersInBlackList = daoService.getListPhoneNumbersInBlackList();
  		 Set<String> setPhoneNumbersInBlackList = new HashSet<>();
  		 for (Blacklist bl : listPhoneNumbersInBlackList) {
  				setPhoneNumbersInBlackList.add(bl.getPhone());
  			}
  		return setPhoneNumbersInBlackList;
  	}
docs: Test if a phone number is already in the black list.
  @param phoneNumber
  @return return true if the phone number is in the bl, false otherwise