The central bank's decision not to allow conventional banks to convert into Islamic banks has frustrated half a dozen lenders. Even conventional banks, which were earlier permitted to open branches or windows for Islamic banking, are not allowed to do it anymore. Bangladesh Bank will not entertain their demand, SK Sur Chowdhury, deputy governor of Bangladesh Bank, said yesterday. The banks that are now awaiting the licence to become Islamic Shariah-based banks should have taken their original permits as Islamic banks instead of conventional ones, he said. Some of the applications have been pending for more than two years now.