lSome verbs, for example decir and insistir have more than one use. They can be used to express a command, a will or wish, but also to simply convey information. In the first case they are followed by a subjunctive and in the second case there is no subjunctive:
lJuan le dice a su hermana que cante. (Juan tell his sister to sing.) = wish or will = Subjunctive
lJuan dice que su hermana canta bien. (Juan says that his sister sings well.) = mentioning something = No Subjunctive.