What is the ruling on working in the Islamic banking services department at the National Commercial Bank?

We have no knowledge of the extent to which the transactions of the aforementioned bank conform to Sharia, so we cannot rule on the permissibility or prohibition of working there. Financial institutions must adhere to certain regulations for working with them to be permissible, the most important of which is that their transactions genuinely conform to Islamic Sharia, not merely as a slogan. What matters are the facts, not the titles.