I heard that it is not appropriate to call women or girls "小姐" in northen China. It is considered rough and have meaning close to hooker. So I never address girl or women "小姐" in north and even when I am in Shanghai or even more southern regions.
Is it really an issue? And if it is, what should I use instead? Right now I always use 姐 or 大姐 just to be sure I dont "hurt" some one.