different shipping charges for cities

Hello there, I am having a problem here. My business resides in Karachi, Pakistan, but I deliver nationwide. I want to charges 150 rupees shipping charges for orders within Karachi and 230 rupees for order anywhere in Pakistan except Karachi. The thing is that Postal codes are not widely used in Pakistan, more than half the people don’t even know their postal code. Can I get a solution to my problem.
150 rupees when city = Karachi
230 rupees when city != Karachi
Thanks in advance